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Lesson 1: Types of RNA, Genetic Code and Protein Translation/
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Full Exam & Question Bank: Lesson 1: Types of RNA, Genetic Code and Protein Translation
617 standard ministerial MCQs measuring key competencies with step-by-step navigation and organized palette.
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Question 1 of 617
Official Ministerial Exam Question • High-Order Thinking
The stop codons that signal termination of translation on an mRNA molecule include:
A
AUG, UAA, UGA
B
UAA, UAG, UGA
C
UAC, UGG, UAA
D
GUA, CAU, UAG
Question 2 of 617
Official Ministerial Exam Question • High-Order Thinking
In a young herbaceous stem, the main force that keeps the plant upright is:
A
lignin in the xylem
B
turgor pressure of the cells
C
the cork layer
D
the root system only
Question 3 of 617
Official Ministerial Exam Question • High-Order Thinking
The waterproof substance deposited on the outer walls of epidermal cells is:
A
lignin
B
suberin
C
cutin
D
cellulose
Question 4 of 617
Official Ministerial Exam Question • High-Order Thinking
Suberin is found in the walls of:
A
cork cells
B
guard cells
C
collenchyma
D
root hairs
Question 5 of 617
Official Ministerial Exam Question • High-Order Thinking
Collenchyma cells are thickened with:
A
lignin
B
cellulose
C
cutin
D
suberin
Question 6 of 617
Official Ministerial Exam Question • High-Order Thinking
Which tissue forms the tough fibres of a celery stalk?
A
parenchyma
B
epidermis
C
sclerenchyma
D
phloem sieve tubes
Question 7 of 617
Official Ministerial Exam Question • High-Order Thinking
A plant that has lost water becomes limp because:
A
its lignin dissolves
B
its cells lose turgor
C
its cellulose is digested
D
its cuticle is removed
Question 8 of 617
Official Ministerial Exam Question • High-Order Thinking
The type of skeleton found in an earthworm is:
A
exoskeleton
B
endoskeleton
C
hydrostatic skeleton
D
cartilage only
Question 9 of 617
Official Ministerial Exam Question • High-Order Thinking
The total number of bones in the adult human skeleton is:
A
33
B
206
C
620
D
300
Question 10 of 617
Official Ministerial Exam Question • High-Order Thinking
The axial skeleton includes:
A
the skull, vertebral column and thoracic cage
B
the pectoral girdle and arm bones
C
the pelvic girdle and leg bones
D
the girdles only
Question 11 of 617
Official Ministerial Exam Question • High-Order Thinking
The number of cervical vertebrae in man is:
A
5
B
7
C
12
D
4
Question 12 of 617
Official Ministerial Exam Question • High-Order Thinking
The largest vertebrae are found in the:
A
cervical region
B
thoracic region
C
lumbar region
D
coccygeal region
Question 13 of 617
Official Ministerial Exam Question • High-Order Thinking
Which vertebrae are fused together?
A
cervical and thoracic
B
thoracic and lumbar
C
lumbar and sacral only
D
sacral and coccygeal
Question 14 of 617
Official Ministerial Exam Question • High-Order Thinking
The spinal cord passes through the:
A
neural canal
B
centrum
C
transverse process
D
neural spine
Question 15 of 617
Official Ministerial Exam Question • High-Order Thinking
The large opening at the base of the skull is the:
A
foramen magnum
B
acetabulum
C
glenoid cavity
D
pubic symphysis
Question 16 of 617
Official Ministerial Exam Question • High-Order Thinking
The number of bones forming the facial part of the skull is:
A
8
B
12
C
14
D
22
Question 17 of 617
Official Ministerial Exam Question • High-Order Thinking
The floating ribs are:
A
the first two pairs
B
the last two pairs
C
the middle two pairs
D
all 12 pairs
Question 18 of 617
Official Ministerial Exam Question • High-Order Thinking
The bone that fits into the glenoid cavity is the head of the:
A
femur
B
humerus
C
radius
D
clavicle
Question 19 of 617
Official Ministerial Exam Question • High-Order Thinking
The forearm is supported by:
A
humerus only
B
tibia and fibula
C
radius and ulna
D
scapula and clavicle
Question 20 of 617
Official Ministerial Exam Question • High-Order Thinking
How many phalanges does the thumb have?
A
1
B
2
C
3
D
4
Question 21 of 617
Official Ministerial Exam Question • High-Order Thinking
The wrist is formed of:
A
5 metacarpals
B
8 carpals
C
7 tarsals
D
14 phalanges
Question 22 of 617
Official Ministerial Exam Question • High-Order Thinking
The acetabulum is the cavity of the:
A
pectoral girdle
B
skull
C
pelvic girdle
D
elbow
Question 23 of 617
Official Ministerial Exam Question • High-Order Thinking
The bone in front of the knee joint is the:
A
patella
B
fibula
C
tarsal
D
scapula
Question 24 of 617
Official Ministerial Exam Question • High-Order Thinking
Cartilage obtains its food and oxygen by:
A
blood vessels inside it
B
diffusion from nearby tissues
C
phagocytosis
D
active transport from muscle
Question 25 of 617
Official Ministerial Exam Question • High-Order Thinking
The joints between the skull bones are:
A
fibrous
B
cartilaginous
C
synovial ball-and-socket
D
hinge
Question 26 of 617
Official Ministerial Exam Question • High-Order Thinking
Which is a ball-and-socket joint?
A
elbow
B
knee
C
hip
D
between vertebrae
Question 27 of 617
Official Ministerial Exam Question • High-Order Thinking
The fluid that lubricates synovial joints is:
A
synovial fluid
B
lymph
C
bile
D
cerebrospinal fluid
Question 28 of 617
Official Ministerial Exam Question • High-Order Thinking
Ligaments connect:
A
muscle to bone
B
bone to bone
C
muscle to muscle
D
skin to muscle
Question 29 of 617
Official Ministerial Exam Question • High-Order Thinking
The Achilles tendon connects the:
A
biceps to radius
B
gastrocnemius muscle to the heel bone
C
quadriceps to the patella
D
femur to tibia
Question 30 of 617
Official Ministerial Exam Question • High-Order Thinking
The leaflets of Mimosa fold when touched. This movement is called:
A
tropism
B
cytoplasmic streaming
C
touch movement
D
pulling movement
Question 31 of 617
Official Ministerial Exam Question • High-Order Thinking
A tendril twines round a support because:
A
the side touching the support grows faster
B
the side away from the support grows faster
C
the tendril cells die on one side
D
the whole tendril contracts
Question 32 of 617
Official Ministerial Exam Question • High-Order Thinking
Corms and bulbs are kept at a suitable depth in the soil by:
A
tendrils
B
pulling (contractile) roots
C
thorns
D
rhizoids
Question 33 of 617
Official Ministerial Exam Question • High-Order Thinking
Cytoplasmic streaming is easily observed in the leaf cells of:
A
Mimosa
B
pea
C
Elodea
D
onion bulb
Question 34 of 617
Official Ministerial Exam Question • High-Order Thinking
The systems that coordinate to produce movement in man are:
A
skeletal, nervous and muscular
B
skeletal, digestive and circulatory
C
muscular, respiratory and nervous
D
nervous, endocrine and excretory
Question 35 of 617
Official Ministerial Exam Question • High-Order Thinking
Each muscle fibre is:
A
uninucleate
B
multinucleated
C
without a membrane
D
without myofibrils
Question 36 of 617
Official Ministerial Exam Question • High-Order Thinking
The cell membrane of a muscle fibre is called:
A
sarcoplasm
B
sarcolemma
C
perimysium
D
myofibril
Question 37 of 617
Official Ministerial Exam Question • High-Order Thinking
The thin filaments of a myofibril are made of:
A
myosin
B
actin
C
keratin
D
collagen
Question 38 of 617
Official Ministerial Exam Question • High-Order Thinking
The distance between two successive Z-lines is a:
A
myofibril
B
sarcomere
C
fascicle
D
H-zone
Question 39 of 617
Official Ministerial Exam Question • High-Order Thinking
The transmitter that carries the impulse across the neuromuscular junction is:
A
cholinesterase
B
acetylcholine
C
adrenaline
D
thyroxine
Question 40 of 617
Official Ministerial Exam Question • High-Order Thinking
Acetylcholine is broken down by cholinesterase into:
A
glucose and fructose
B
choline and acetic acid
C
lactic acid and CO2
D
amino acids
Question 41 of 617
Official Ministerial Exam Question • High-Order Thinking
When a muscle contracts, which band does NOT change in length?
A
I-band
B
H-zone
C
A-band
D
distance between Z-lines
Question 42 of 617
Official Ministerial Exam Question • High-Order Thinking
The immediate source of energy for muscle contraction is:
A
glycogen
B
glucose
C
ATP
D
lactic acid
Question 43 of 617
Official Ministerial Exam Question • High-Order Thinking
Muscle fatigue is caused by accumulation of:
A
carbon dioxide
B
lactic acid
C
acetic acid
D
urea
Question 44 of 617
Official Ministerial Exam Question • High-Order Thinking
Endocrine glands release their secretions:
A
through ducts into the intestine
B
through ducts to the outside
C
directly into the blood
D
into the lymph nodes only
Question 45 of 617
Official Ministerial Exam Question • High-Order Thinking
Who discovered the first animal hormone (secretin) and coined the word hormone?
A
Jensen
B
Starling
C
Huxley
D
Banting
Question 46 of 617
Official Ministerial Exam Question • High-Order Thinking
In Starling's experiment the pancreas still secreted juice after its nerves were cut. This proved that:
A
the pancreas secretes without any stimulus
B
a non-nervous (chemical) stimulus exists
C
nerves are useless
D
the stomach controls the pancreas
Question 47 of 617
Official Ministerial Exam Question • High-Order Thinking
The word "hormone" means:
A
to digest
B
to build
C
to activate or excite
D
to protect
Question 48 of 617
Official Ministerial Exam Question • High-Order Thinking
Jensen explained phototropism using:
A
thyroxine
B
auxins
C
insulin
D
oxytocin
Question 49 of 617
Official Ministerial Exam Question • High-Order Thinking
Plant hormones (auxins) are produced by:
A
special glands
B
tips of coleoptiles and buds
C
roots only
D
the cuticle
Question 50 of 617
Official Ministerial Exam Question • High-Order Thinking
Hormones are secreted in:
A
grams
B
milligrams
C
micrograms (very small amounts)
D
kilograms
Question 51 of 617
Official Ministerial Exam Question • High-Order Thinking
Which hormone is a steroid?
A
insulin
B
thyroxine
C
progesterone
D
glucagon
Question 52 of 617
Official Ministerial Exam Question • High-Order Thinking
Which of the following is a mixed gland?
A
thyroid
B
pancreas
C
pituitary
D
adrenal
Question 53 of 617
Official Ministerial Exam Question • High-Order Thinking
The pituitary gland is joined to the brain by the:
A
isthmus
B
infundibulum
C
cerebellum
D
corpus callosum
Question 54 of 617
Official Ministerial Exam Question • High-Order Thinking
Which pituitary lobe belongs to the adenohypophysis?
A
posterior lobe
B
anterior lobe
C
infundibulum
D
none of them
Question 55 of 617
Official Ministerial Exam Question • High-Order Thinking
Excess growth hormone in a child causes:
A
dwarfism
B
acromegaly
C
gigantism
D
cretinism
Question 56 of 617
Official Ministerial Exam Question • High-Order Thinking
Acromegaly is characterised by:
A
very tall stature with normal proportions
B
enlarged hands, feet and face bones in an adult
C
dry skin and weight gain
D
protruding eyeballs
Question 57 of 617
Official Ministerial Exam Question • High-Order Thinking
The hormone that stimulates milk secretion from the mammary glands is:
A
oxytocin
B
prolactin
C
progesterone
D
ADH
Question 58 of 617
Official Ministerial Exam Question • High-Order Thinking
Which hormone stimulates the adrenal cortex?
A
TSH
B
ACTH
C
FSH
D
LH
Question 59 of 617
Official Ministerial Exam Question • High-Order Thinking
The hormones of the posterior lobe are made in the:
A
liver
B
hypothalamus
C
thyroid
D
adrenal medulla
Question 60 of 617
Official Ministerial Exam Question • High-Order Thinking
ADH acts on:
A
the liver
B
the kidney tubules
C
the pancreas
D
the thyroid
Question 61 of 617
Official Ministerial Exam Question • High-Order Thinking
The hormone used by doctors to accelerate delivery is:
A
oxytocin
B
prolactin
C
FSH
D
thyroxine
Question 62 of 617
Official Ministerial Exam Question • High-Order Thinking
FSH in the male stimulates:
A
the interstitial cells to make testosterone
B
the seminiferous tubules to produce sperms
C
the prostate gland
D
the adrenal gland
Question 63 of 617
Official Ministerial Exam Question • High-Order Thinking
The thyroid gland lies:
A
behind the stomach
B
above the kidneys
C
in the neck in front of the trachea
D
under the brain
Question 64 of 617
Official Ministerial Exam Question • High-Order Thinking
The element essential for the manufacture of thyroxine is:
A
calcium
B
iron
C
iodine
D
sodium
Question 65 of 617
Official Ministerial Exam Question • High-Order Thinking
Cretinism results from:
A
hyposecretion of thyroxine in childhood
B
hypersecretion of thyroxine in an adult
C
hypersecretion of GH in childhood
D
lack of insulin
Question 66 of 617
Official Ministerial Exam Question • High-Order Thinking
Dry skin, hair loss, obesity and intolerance to cold in an adult indicate:
A
exophthalmic goitre
B
myxoedema
C
acromegaly
D
diabetes mellitus
Question 67 of 617
Official Ministerial Exam Question • High-Order Thinking
Protruding eyeballs, weight loss and rapid heartbeat are symptoms of:
A
simple goitre
B
cretinism
C
exophthalmic goitre
D
tetany
Question 68 of 617
Official Ministerial Exam Question • High-Order Thinking
The hormone that lowers blood calcium is:
A
parathormone
B
calcitonin
C
aldosterone
D
insulin
Question 69 of 617
Official Ministerial Exam Question • High-Order Thinking
Hypersecretion of parathormone leads to:
A
muscle spasms
B
fragile bones
C
goitre
D
dwarfism
Question 70 of 617
Official Ministerial Exam Question • High-Order Thinking
Painful muscular convulsions result from:
A
hypoparathyroidism
B
hyperparathyroidism
C
hyperthyroidism
D
hypersecretion of GH
Question 71 of 617
Official Ministerial Exam Question • High-Order Thinking
Aldosterone mainly regulates:
A
blood glucose
B
sodium and potassium balance
C
calcium
D
body growth
Question 72 of 617
Official Ministerial Exam Question • High-Order Thinking
The hormone secreted in emergency (fight and flight) is:
A
adrenaline
B
cortisone
C
insulin
D
progesterone
Question 73 of 617
Official Ministerial Exam Question • High-Order Thinking
Adrenaline increases blood glucose by:
A
converting glucose to glycogen
B
breaking down liver glycogen
C
stopping glucose uptake by cells
D
inhibiting insulin receptors only
Question 74 of 617
Official Ministerial Exam Question • High-Order Thinking
Cortisone belongs to the group of:
A
mineralocorticoids
B
glucocorticoids
C
sex hormones
D
amino-acid hormones
Question 75 of 617
Official Ministerial Exam Question • High-Order Thinking
A tumour of the adrenal cortex in a woman may cause:
A
feminisation
B
masculinisation
C
goitre
D
dwarfism
Question 76 of 617
Official Ministerial Exam Question • High-Order Thinking
Insulin is secreted by:
A
alpha cells
B
beta cells of the islets of Langerhans
C
pancreatic acini
D
the adrenal cortex
Question 77 of 617
Official Ministerial Exam Question • High-Order Thinking
The normal blood glucose level is about:
A
8-12 mg/100 cm3
B
80-120 mg/100 cm3
C
300-400 mg/100 cm3
D
800-1200 mg/100 cm3
Question 78 of 617
Official Ministerial Exam Question • High-Order Thinking
Glucagon increases blood glucose by converting glycogen into glucose in the:
A
muscles
B
liver only
C
kidney
D
intestine
Question 79 of 617
Official Ministerial Exam Question • High-Order Thinking
Which sugar enters cells without needing insulin, according to the book?
A
glucose
B
galactose
C
fructose
D
mannose
Question 80 of 617
Official Ministerial Exam Question • High-Order Thinking
A diabetic patient has continuous thirst because:
A
the kidney stops working
B
glucose in the urine draws water out, causing large urine volumes
C
the sweat glands are over-active
D
insulin is stored in the kidney
Question 81 of 617
Official Ministerial Exam Question • High-Order Thinking
The male sex hormones are secreted by the:
A
Sertoli cells
B
interstitial cells of the testes
C
prostate gland
D
seminal vesicles
Question 82 of 617
Official Ministerial Exam Question • High-Order Thinking
The hormone that relaxes the pubic symphysis at the end of pregnancy is:
A
progesterone
B
oestrogen
C
relaxin
D
oxytocin
Question 83 of 617
Official Ministerial Exam Question • High-Order Thinking
Cholecystokinin causes:
A
gastric juice secretion
B
contraction of the gall bladder
C
secretion of insulin
D
release of bile salts into blood
Question 84 of 617
Official Ministerial Exam Question • High-Order Thinking
Which hormone is secreted by the stomach wall?
A
secretin
B
gastrin
C
CCK
D
insulin
Question 85 of 617
Official Ministerial Exam Question • High-Order Thinking
Compared with the nervous system, hormonal control is:
A
faster and shorter in effect
B
slower and longer in effect
C
faster and longer in effect
D
slower and shorter in effect
Question 86 of 617
Official Ministerial Exam Question • High-Order Thinking
Reproduction is essential for:
A
the life of each individual
B
the continuity of the species
C
respiration
D
digestion
Question 87 of 617
Official Ministerial Exam Question • High-Order Thinking
Which organisms usually produce the largest number of offspring?
A
mammals
B
birds
C
parasites and aquatic animals
D
primates
Question 88 of 617
Official Ministerial Exam Question • High-Order Thinking
Asexual reproduction depends on:
A
meiosis
B
mitosis
C
fertilisation
D
crossing over
Question 89 of 617
Official Ministerial Exam Question • High-Order Thinking
Reproduction in Amoeba is by:
A
budding
B
binary fission
C
spores
D
conjugation
Question 90 of 617
Official Ministerial Exam Question • High-Order Thinking
In yeast, the new individual arises as a:
A
spore
B
bud
C
gamete
D
zygote
Question 91 of 617
Official Ministerial Exam Question • High-Order Thinking
The bud of Hydra arises by division of:
A
interstitial cells
B
nerve cells
C
stinging cells
D
gland cells
Question 92 of 617
Official Ministerial Exam Question • High-Order Thinking
An animal that regenerates a whole body from a piece is:
A
frog
B
Planaria
C
rabbit
D
bird
Question 93 of 617
Official Ministerial Exam Question • High-Order Thinking
Which organism reproduces by spores?
A
Hydra
B
bread mould
C
Planaria
D
Amoeba
Question 94 of 617
Official Ministerial Exam Question • High-Order Thinking
Drones of the honey bee are:
A
diploid, from fertilised eggs
B
haploid, from unfertilised eggs
C
triploid
D
female
Question 95 of 617
Official Ministerial Exam Question • High-Order Thinking
Tissue culture proves that any plant somatic cell:
A
lacks genes
B
carries the complete genetic information
C
cannot divide
D
is haploid
Question 96 of 617
Official Ministerial Exam Question • High-Order Thinking
The liquid that supplied nutrients and hormones in the carrot tissue culture experiment was:
A
cow milk
B
coconut milk
C
blood plasma
D
honey solution
Question 97 of 617
Official Ministerial Exam Question • High-Order Thinking
Conjugation occurs in:
A
Spirogyra
B
Amoeba
C
Hydra
D
Planaria
Question 98 of 617
Official Ministerial Exam Question • High-Order Thinking
The cells of a Spirogyra filament are:
A
diploid
B
haploid
C
triploid
D
tetraploid
Question 99 of 617
Official Ministerial Exam Question • High-Order Thinking
The zygote of Spirogyra with a thick wall is the:
A
oocyst
B
zygospore
C
ookinete
D
blastocyst
Question 100 of 617
Official Ministerial Exam Question • High-Order Thinking
Fertilisation is external in:
A
reptiles
B
birds
C
bony fish and frogs
D
mammals
Question 101 of 617
Official Ministerial Exam Question • High-Order Thinking
The infective stage that the mosquito injects into man is the:
A
merozoite
B
sporozoite
C
gametocyte
D
ookinete
Question 102 of 617
Official Ministerial Exam Question • High-Order Thinking
The sexual generation of Plasmodium takes place in:
A
human liver
B
human red blood cells
C
female Anopheles
D
male Anopheles
Question 103 of 617
Official Ministerial Exam Question • High-Order Thinking
Malaria fever appears when:
A
sporozoites enter the blood
B
merozoites burst out of red blood cells
C
gametocytes form
D
the oocyst forms
Question 104 of 617
Official Ministerial Exam Question • High-Order Thinking
In ferns, the spores are produced by meiosis in the:
A
gametophyte
B
sporophyte
C
archegonium
D
antheridium
Question 105 of 617
Official Ministerial Exam Question • High-Order Thinking
The male sex organs of a fern gametophyte are the:
A
archegonia
B
antheridia
C
sori
D
rhizoids
Question 106 of 617
Official Ministerial Exam Question • High-Order Thinking
The male part of a flower is the:
A
gynoecium
B
androecium
C
calyx
D
corolla
Question 107 of 617
Official Ministerial Exam Question • High-Order Thinking
The part of the carpel that receives pollen is the:
A
ovary
B
style
C
stigma
D
micropyle
Question 108 of 617
Official Ministerial Exam Question • High-Order Thinking
The calyx is formed of:
A
petals
B
sepals
C
stamens
D
carpels
Question 109 of 617
Official Ministerial Exam Question • High-Order Thinking
Each pollen mother cell gives:
A
2 pollen grains
B
4 pollen grains
C
8 pollen grains
D
1 pollen grain
Question 110 of 617
Official Ministerial Exam Question • High-Order Thinking
A mature pollen grain before germination contains:
A
one nucleus
B
tube nucleus and generative nucleus
C
three nuclei
D
four nuclei
Question 111 of 617
Official Ministerial Exam Question • High-Order Thinking
The mature embryo sac contains how many nuclei?
A
4
B
6
C
8
D
16
Question 112 of 617
Official Ministerial Exam Question • High-Order Thinking
The ploidy of the endosperm nucleus is:
A
N
B
2N
C
3N
D
4N
Question 113 of 617
Official Ministerial Exam Question • High-Order Thinking
The pollen tube enters the ovule through the:
A
funicle
B
micropyle
C
stigma
D
style
Question 114 of 617
Official Ministerial Exam Question • High-Order Thinking
The seed coat (testa) develops from the:
A
ovary wall
B
integuments
C
nucellus
D
endosperm
Question 115 of 617
Official Ministerial Exam Question • High-Order Thinking
Which seed is non-endospermic?
A
wheat
B
maize
C
bean
D
castor
Question 116 of 617
Official Ministerial Exam Question • High-Order Thinking
The apple is a false fruit because it develops from the:
A
ovary only
B
receptacle together with the ovary
C
petals
D
stigma
Question 117 of 617
Official Ministerial Exam Question • High-Order Thinking
Seedless banana is formed by:
A
parthenogenesis
B
parthenocarpy
C
budding
D
tissue culture
Question 118 of 617
Official Ministerial Exam Question • High-Order Thinking
The testes lie in the scrotum because:
A
the abdomen is full
B
a lower temperature suits spermatogenesis
C
they secrete hormones there only
D
the scrotum is warmer
Question 119 of 617
Official Ministerial Exam Question • High-Order Thinking
Testosterone is secreted by the:
A
Sertoli cells
B
interstitial cells
C
epididymis
D
seminal vesicles
Question 120 of 617
Official Ministerial Exam Question • High-Order Thinking
The secretion of the seminal vesicles contains:
A
fructose
B
lactose
C
insulin
D
FSH
Question 121 of 617
Official Ministerial Exam Question • High-Order Thinking
In spermatogenesis, the cell that undergoes meiosis I is the:
A
spermatogonium
B
primary spermatocyte
C
secondary spermatocyte
D
spermatid
Question 122 of 617
Official Ministerial Exam Question • High-Order Thinking
The structure that supplies the sperm with energy is the:
A
acrosome
B
mitochondria in the midpiece
C
centrioles
D
nucleus
Question 123 of 617
Official Ministerial Exam Question • High-Order Thinking
The acrosome secretes:
A
amylase
B
hyaluronidase
C
pepsin
D
lipase
Question 124 of 617
Official Ministerial Exam Question • High-Order Thinking
One primary oocyte forms:
A
4 ova
B
2 ova
C
1 ovum and polar bodies
D
3 ova
Question 125 of 617
Official Ministerial Exam Question • High-Order Thinking
Oogonia are formed during the:
A
puberty
B
embryonic stage
C
pregnancy
D
menopause
Question 126 of 617
Official Ministerial Exam Question • High-Order Thinking
In a 28-day cycle ovulation occurs on about day:
A
1
B
7
C
14
D
21
Question 127 of 617
Official Ministerial Exam Question • High-Order Thinking
Ovulation is caused by:
A
FSH
B
LH
C
progesterone
D
prolactin
Question 128 of 617
Official Ministerial Exam Question • High-Order Thinking
The corpus luteum develops from the:
A
endometrium
B
Graafian follicle
C
placenta
D
oviduct
Question 129 of 617
Official Ministerial Exam Question • High-Order Thinking
Fertilisation normally occurs in the:
A
uterus
B
vagina
C
upper third of the Fallopian tube
D
ovary
Question 130 of 617
Official Ministerial Exam Question • High-Order Thinking
The embryo implants in the uterus at the end of:
A
the first day
B
the first week
C
the third month
D
the ninth month
Question 131 of 617
Official Ministerial Exam Question • High-Order Thinking
The amnion contains fluid that:
A
feeds the embryo
B
protects the embryo from shocks and dryness
C
makes hormones
D
removes carbon dioxide
Question 132 of 617
Official Ministerial Exam Question • High-Order Thinking
After the fourth month progesterone is mainly secreted by the:
A
corpus luteum
B
placenta
C
pituitary
D
adrenal
Question 133 of 617
Official Ministerial Exam Question • High-Order Thinking
The contraceptive pill prevents pregnancy by:
A
blocking the oviducts
B
inhibiting ovulation
C
killing sperms in the testes
D
preventing implantation only
Question 134 of 617
Official Ministerial Exam Question • High-Order Thinking
Identical twins result from:
A
two ova and two sperms
B
one ovum and one sperm, then splitting
C
one ovum and two sperms
D
two ova and one sperm
Question 135 of 617
Official Ministerial Exam Question • High-Order Thinking
In vitro fertilisation means fertilisation:
A
in the oviduct
B
in the uterus
C
outside the body in a dish
D
in the ovary
Question 136 of 617
Official Ministerial Exam Question • High-Order Thinking
Dolly the sheep was produced from:
A
a fertilised egg
B
a nucleus from an adult mammary gland cell placed in an enucleated egg
C
a drone
D
parthenocarpy
Question 137 of 617
Official Ministerial Exam Question • High-Order Thinking
X and Y sperms can be separated by:
A
distillation
B
centrifugation or electrophoresis
C
filtration
D
chromatography on paper only
Question 138 of 617
Official Ministerial Exam Question • High-Order Thinking
Immunity is best defined as the ability of an organism to:
A
produce hormones
B
resist pathogens through its immune system
C
digest food rapidly
D
avoid all contact with microbes
Question 139 of 617
Official Ministerial Exam Question • High-Order Thinking
Which pair correctly names the two cooperating immune systems of animals?
A
Structural and biochemical
B
Primary and secondary
C
Innate and acquired
D
Humoral and hormonal
Question 140 of 617
Official Ministerial Exam Question • High-Order Thinking
A waxy layer of cutin on leaves helps defence because it:
A
absorbs water for fungi
B
prevents water settling, so microbes cannot grow easily
C
kills bacteria with toxins
D
is made of lignin
Question 141 of 617
Official Ministerial Exam Question • High-Order Thinking
Cork cell walls are thickened with:
A
cellulose only
B
chitin
C
suberin
D
pectin only
Question 142 of 617
Official Ministerial Exam Question • High-Order Thinking
Tyloses are outgrowths of:
A
sieve tubes into phloem
B
parenchyma protoplasts into xylem vessels
C
epidermal cells into the cuticle
D
root hairs into the soil
Question 143 of 617
Official Ministerial Exam Question • High-Order Thinking
Which of these is a biochemical (not structural) defence in plants?
A
Gum deposition
B
Tylosis formation
C
Phenol production
D
Cork formation
Question 144 of 617
Official Ministerial Exam Question • High-Order Thinking
Canavanine is an example of:
A
a plant hormone
B
a non-protein amino acid toxic to pathogens
C
a structural protein
D
a detoxifying enzyme
Question 145 of 617
Official Ministerial Exam Question • High-Order Thinking
Deliberate death of tissue around an infection, so the pathogen cannot spread, is called:
A
tylosis
B
hypersensitive response
C
inducible defence
D
detoxification
Question 146 of 617
Official Ministerial Exam Question • High-Order Thinking
Gum deposition after wounding is seen in:
A
Acacia nilotica
B
maize
C
cactus
D
wheat
Question 147 of 617
Official Ministerial Exam Question • High-Order Thinking
The main component of the human immune system is the:
A
endocrine system
B
lymphatic system
C
digestive system
D
skeletal system
Question 148 of 617
Official Ministerial Exam Question • High-Order Thinking
Primary lymphoid organs are:
A
spleen and tonsils
B
lymph nodes and appendix
C
bone marrow and thymus
D
Peyer's patches and spleen
Question 149 of 617
Official Ministerial Exam Question • High-Order Thinking
T lymphocytes complete their maturation in the:
A
bone marrow
B
spleen
C
thymus gland
D
tonsils
Question 150 of 617
Official Ministerial Exam Question • High-Order Thinking
The thymus gland is located:
A
in the neck beside the thyroid
B
behind the sternum, in front of the trachea above the heart
C
in the upper left abdomen
D
in the lining of the small intestine
Question 151 of 617
Official Ministerial Exam Question • High-Order Thinking
Which organ breaks down worn-out red blood cells using macrophages?
A
Tonsils
B
Thymus
C
Spleen
D
Lymph node
Question 152 of 617
Official Ministerial Exam Question • High-Order Thinking
Peyer's patches are found in:
A
the stomach wall
B
the lower small intestine
C
the neck
D
the pharynx
Question 153 of 617
Official Ministerial Exam Question • High-Order Thinking
Lymph nodes:
A
filter lymph and store lymphocytes
B
secrete thymosin
C
produce red blood cells in adults
D
digest food
Question 154 of 617
Official Ministerial Exam Question • High-Order Thinking
Which of the following is an agranulocyte?
A
Neutrophil
B
Eosinophil
C
Basophil
D
Lymphocyte
Question 155 of 617
Official Ministerial Exam Question • High-Order Thinking
Cells that secrete antibodies are:
A
plasma cells
B
cytotoxic T cells
C
NK cells
D
macrophages
Question 156 of 617
Official Ministerial Exam Question • High-Order Thinking
The T cells that stimulate B cells to make antibodies are:
A
suppressor T cells
B
helper T cells
C
cytotoxic T cells
D
memory B cells
Question 157 of 617
Official Ministerial Exam Question • High-Order Thinking
Perforin is a protein that:
A
neutralises toxins
B
forms pores in target cell membranes
C
carries amino acids
D
stimulates histamine release
Question 158 of 617
Official Ministerial Exam Question • High-Order Thinking
Natural killer cells mature in the:
A
thymus
B
bone marrow
C
spleen
D
lymph nodes
Question 159 of 617
Official Ministerial Exam Question • High-Order Thinking
Monocytes change into:
A
plasma cells
B
mast cells
C
macrophages
D
T cells
Question 160 of 617
Official Ministerial Exam Question • High-Order Thinking
Antigens are usually:
A
lipids of the host
B
proteins or glycoproteins on the pathogen surface
C
hormones
D
antibiotics
Question 161 of 617
Official Ministerial Exam Question • High-Order Thinking
Interferons are secreted by:
A
healthy bacteria
B
virus-infected cells
C
plasma cells
D
red blood cells
Question 162 of 617
Official Ministerial Exam Question • High-Order Thinking
Proteins that attract phagocytes to the site of infection are:
A
interleukins
B
chemokines
C
interferons
D
complements
Question 163 of 617
Official Ministerial Exam Question • High-Order Thinking
Which class of immunoglobulin is NOT one of the five?
A
IgG
B
IgM
C
IgK
D
IgE
Question 164 of 617
Official Ministerial Exam Question • High-Order Thinking
An antibody molecule is made of:
A
one polypeptide chain
B
two light chains only
C
two heavy and two light chains
D
four identical heavy chains
Question 165 of 617
Official Ministerial Exam Question • High-Order Thinking
The specificity of an antibody depends on:
A
the constant region
B
the hinge only
C
the amino acids of the variable regions
D
the number of heavy chains
Question 166 of 617
Official Ministerial Exam Question • High-Order Thinking
The number of antigen-binding sites on one antibody (IgG) is:
A
1
B
2
C
3
D
4
Question 167 of 617
Official Ministerial Exam Question • High-Order Thinking
Clumping of microbes by IgM is called:
A
precipitation
B
neutralisation
C
agglutination
D
lysis
Question 168 of 617
Official Ministerial Exam Question • High-Order Thinking
Antibodies protect against viruses mainly by:
A
neutralisation
B
agglutination only
C
perforin release
D
histamine release
Question 169 of 617
Official Ministerial Exam Question • High-Order Thinking
Which of these belongs to the first line of defence?
A
Inflammation
B
Gastric hydrochloric acid
C
Plasma cells
D
Memory cells
Question 170 of 617
Official Ministerial Exam Question • High-Order Thinking
Histamine is released by:
A
mast cells and basophils
B
B cells
C
neutrophils only
D
red blood cells
Question 171 of 617
Official Ministerial Exam Question • High-Order Thinking
Histamine causes blood vessels to:
A
constrict and become less permeable
B
dilate and become more permeable
C
clot
D
disintegrate
Question 172 of 617
Official Ministerial Exam Question • High-Order Thinking
Cilia in the respiratory tract:
A
make mucus
B
sweep mucus with trapped microbes out
C
kill microbes with enzymes
D
produce antibodies
Question 173 of 617
Official Ministerial Exam Question • High-Order Thinking
Helper T cells recognise antigen when it is presented:
A
free in plasma
B
on MHC proteins on macrophages
C
on red blood cells
D
bound to antibodies
Question 174 of 617
Official Ministerial Exam Question • High-Order Thinking
Antibodies are not effective against viruses inside cells because they:
A
are destroyed in the lymph
B
are too large to enter the cells
C
bind only to bacteria
D
are produced too slowly
Question 175 of 617
Official Ministerial Exam Question • High-Order Thinking
After the pathogen has been destroyed, the immune response is limited by:
A
helper T cells
B
cytotoxic T cells
C
suppressor T cells
D
macrophages
Question 176 of 617
Official Ministerial Exam Question • High-Order Thinking
The secondary immune response is faster because of:
A
more macrophages
B
memory cells
C
more interferon
D
thicker skin
Question 177 of 617
Official Ministerial Exam Question • High-Order Thinking
Which statement about memory cells is correct?
A
They live a few days
B
They are made only by NK cells
C
They may survive for tens of years
D
They are made only after the second infection
Question 178 of 617
Official Ministerial Exam Question • High-Order Thinking
Chromosomes are made of:
A
DNA and lipids
B
DNA and proteins
C
RNA and carbohydrates
D
proteins only
Question 179 of 617
Official Ministerial Exam Question • High-Order Thinking
Scientists first expected proteins to be the genetic material because proteins:
A
are more stable than DNA
B
are built from 20 amino acids and are more varied
C
are found only in the nucleus
D
contain phosphorus
Question 180 of 617
Official Ministerial Exam Question • High-Order Thinking
Griffith worked with:
A
E. coli and phages
B
Pneumococcus and mice
C
yeast and fruit flies
D
tobacco mosaic virus
Question 181 of 617
Official Ministerial Exam Question • High-Order Thinking
Mice injected with heat-killed S bacteria mixed with live R bacteria:
A
all survived
B
some died and live S bacteria were recovered
C
died with only R bacteria found
D
developed immunity
Question 182 of 617
Official Ministerial Exam Question • High-Order Thinking
The enzyme used by Avery's group to show DNA was the transforming material was:
A
protease
B
RNase
C
deoxyribonuclease
D
lipase
Question 183 of 617
Official Ministerial Exam Question • High-Order Thinking
In the Hershey–Chase experiment the phage protein was labelled with:
A
³²P
B
³⁵S
C
¹⁴C
D
³H
Question 184 of 617
Official Ministerial Exam Question • High-Order Thinking
Hershey and Chase found radioactivity from ³²P:
A
outside the bacteria
B
inside the bacteria
C
in neither
D
only in the phage coat
Question 185 of 617
Official Ministerial Exam Question • High-Order Thinking
The genetic material of the AIDS virus is:
A
DNA
B
RNA
C
protein
D
lipid
Question 186 of 617
Official Ministerial Exam Question • High-Order Thinking
Compared with a somatic cell, a gamete contains DNA amounting to:
A
double
B
the same
C
half
D
one quarter
Question 187 of 617
Official Ministerial Exam Question • High-Order Thinking
The sugar of DNA is:
A
ribose
B
glucose
C
deoxyribose
D
fructose
Question 188 of 617
Official Ministerial Exam Question • High-Order Thinking
Which pair contains only purines?
A
A and T
B
A and G
C
C and T
D
G and C
Question 189 of 617
Official Ministerial Exam Question • High-Order Thinking
The phosphate group of a nucleotide is bonded to carbon number … of the sugar:
A
1′
B
2′
C
3′
D
5′
Question 190 of 617
Official Ministerial Exam Question • High-Order Thinking
Number of hydrogen bonds between guanine and cytosine:
A
1
B
2
C
3
D
4
Question 191 of 617
Official Ministerial Exam Question • High-Order Thinking
If a DNA molecule has 20% thymine, its guanine content is:
A
20%
B
30%
C
40%
D
60%
Question 192 of 617
Official Ministerial Exam Question • High-Order Thinking
Franklin used … to study DNA:
A
electron microscopy
B
X-ray diffraction
C
chromatography
D
centrifugation
Question 193 of 617
Official Ministerial Exam Question • High-Order Thinking
Which statement about the DNA double helix is correct?
A
Strands are parallel
B
Bases face outward
C
Strands are antiparallel
D
A pairs with C
Question 194 of 617
Official Ministerial Exam Question • High-Order Thinking
The number of base pairs per helical turn is about:
A
3
B
5
C
10
D
20
Question 195 of 617
Official Ministerial Exam Question • High-Order Thinking
All rungs of the DNA ladder have equal width because each pairs:
A
two purines
B
two pyrimidines
C
a purine with a pyrimidine
D
a base with a sugar
Question 196 of 617
Official Ministerial Exam Question • High-Order Thinking
The enzyme that separates the DNA strands is:
A
ligase
B
helicase
C
primase
D
polymerase
Question 197 of 617
Official Ministerial Exam Question • High-Order Thinking
DNA polymerase adds nucleotides to the … end of the new strand:
A
5′
B
3′
C
both ends
D
the middle
Question 198 of 617
Official Ministerial Exam Question • High-Order Thinking
Primase synthesises short pieces of:
A
DNA
B
protein
C
RNA
D
lipid
Question 199 of 617
Official Ministerial Exam Question • High-Order Thinking
Okazaki fragments are found on the:
A
leading strand
B
lagging strand
C
both equally
D
RNA only
Question 200 of 617
Official Ministerial Exam Question • High-Order Thinking
Okazaki fragments are joined by:
A
helicase
B
primase
C
DNA ligase
D
RNA polymerase
Question 201 of 617
Official Ministerial Exam Question • High-Order Thinking
Each DNA molecule after replication contains:
A
two old strands
B
two new strands
C
one old and one new strand
D
mixed fragments of old and new
Question 202 of 617
Official Ministerial Exam Question • High-Order Thinking
Replication in eukaryotes starts at:
A
one point
B
the telomeres only
C
hundreds or thousands of points
D
the centromere only
Question 203 of 617
Official Ministerial Exam Question • High-Order Thinking
In prokaryotes, replication begins:
A
at many sites
B
at the point of attachment of DNA to the plasma membrane
C
in the nucleolus
D
in the ribosomes
Question 204 of 617
Official Ministerial Exam Question • High-Order Thinking
About how many purine bases are lost daily from each human cell's DNA?
A
50
B
500
C
5,000
D
5 million
Question 205 of 617
Official Ministerial Exam Question • High-Order Thinking
DNA repair needs:
A
both strands damaged
B
one intact strand as template
C
RNA primers only
D
histones
Question 206 of 617
Official Ministerial Exam Question • High-Order Thinking
Why do RNA viruses mutate rapidly?
A
They have no genes
B
Single-stranded RNA cannot be repaired
C
They have histones
D
They replicate once
Question 207 of 617
Official Ministerial Exam Question • High-Order Thinking
Plasmids are:
A
small circular DNA molecules in bacteria
B
linear chromosomes
C
ribosomal subunits
D
proteins in chromatin
Question 208 of 617
Official Ministerial Exam Question • High-Order Thinking
Histones are rich in:
A
glutamate and aspartate
B
arginine and lysine
C
cysteine
D
glycine
Question 209 of 617
Official Ministerial Exam Question • High-Order Thinking
The first level of DNA packing is the:
A
chromatid
B
nucleosome
C
loop
D
centromere
Question 210 of 617
Official Ministerial Exam Question • High-Order Thinking
Which has DNA similar to that of prokaryotes?
A
Nucleus
B
Golgi apparatus
C
Mitochondria
D
Lysosomes
Question 211 of 617
Official Ministerial Exam Question • High-Order Thinking
E. coli DNA, if straightened, is about … long:
A
1.4 mm
B
2 μm
C
2 m
D
14 cm
Question 212 of 617
Official Ministerial Exam Question • High-Order Thinking
The total DNA of a cell of an individual is its:
A
karyotype
B
genome
C
plasmid
D
chromatin
Question 213 of 617
Official Ministerial Exam Question • High-Order Thinking
Promoters are found:
A
at the end of genes
B
at the beginning of genes
C
in ribosomes
D
in the cell wall
Question 214 of 617
Official Ministerial Exam Question • High-Order Thinking
The salamander genome is about … times the human genome:
A
3
B
10
C
30
D
300
Question 215 of 617
Official Ministerial Exam Question • High-Order Thinking
Klinefelter syndrome has the chromosome formula:
A
44 + XO
B
44 + XXY
C
45 + XY
D
44 + XYY
Question 216 of 617
Official Ministerial Exam Question • High-Order Thinking
Which agent is used to induce polyploidy?
A
Penicillin
B
Colchicine
C
Insulin
D
Ethanol
Question 217 of 617
Official Ministerial Exam Question • High-Order Thinking
Polyploidy is more common in:
A
mammals
B
plants
C
birds
D
humans
Question 218 of 617
Official Ministerial Exam Question • High-Order Thinking
Collagen and keratin are examples of:
A
enzymes
B
structural proteins
C
hormones
D
antibodies
Question 219 of 617
Official Ministerial Exam Question • High-Order Thinking
Which of these is a regulatory protein?
A
Actin
B
Myosin
C
Insulin
D
Keratin
Question 220 of 617
Official Ministerial Exam Question • High-Order Thinking
The amino acid with a second hydrogen atom as its R group is:
A
alanine
B
glycine
C
serine
D
lysine
Question 221 of 617
Official Ministerial Exam Question • High-Order Thinking
Amino acids are joined by:
A
glycosidic bonds
B
ester bonds
C
peptide bonds
D
phosphodiester bonds
Question 222 of 617
Official Ministerial Exam Question • High-Order Thinking
The sugar of RNA is:
A
deoxyribose
B
ribose
C
glucose
D
fructose
Question 223 of 617
Official Ministerial Exam Question • High-Order Thinking
RNA contains … instead of thymine:
A
adenine
B
cytosine
C
uracil
D
guanine
Question 224 of 617
Official Ministerial Exam Question • High-Order Thinking
A nucleic acid with A 12%, U 18%, G 39%, C 31% is:
A
double-stranded DNA
B
single-stranded DNA
C
RNA
D
can't be known
Question 225 of 617
Official Ministerial Exam Question • High-Order Thinking
Transcription begins when RNA polymerase binds to the:
A
ribosome
B
promoter
C
stop codon
D
anticodon
Question 226 of 617
Official Ministerial Exam Question • High-Order Thinking
RNA polymerase assembles RNA in the direction:
A
3′→5′
B
5′→3′
C
both
D
random
Question 227 of 617
Official Ministerial Exam Question • High-Order Thinking
In eukaryotes the number of RNA polymerases is:
A
one
B
two
C
three
D
four
Question 228 of 617
Official Ministerial Exam Question • High-Order Thinking
The poly‑A tail of mRNA:
A
is translated to lysine
B
protects the mRNA from enzymes
C
binds the ribosome
D
is the start codon
Question 229 of 617
Official Ministerial Exam Question • High-Order Thinking
Ribosomes are produced in the:
A
Golgi
B
nucleolus
C
lysosome
D
mitochondrion
Question 230 of 617
Official Ministerial Exam Question • High-Order Thinking
The number of different rRNA kinds in a ribosome is:
A
1
B
2
C
4
D
20
Question 231 of 617
Official Ministerial Exam Question • High-Order Thinking
The amino acid attaches to the tRNA at the sequence:
A
AUG
B
CCA at the 3′ end
C
anticodon
D
UAA
Question 232 of 617
Official Ministerial Exam Question • High-Order Thinking
The anticodon is found on:
A
mRNA
B
rRNA
C
tRNA
D
DNA
Question 233 of 617
Official Ministerial Exam Question • High-Order Thinking
In prokaryotes transcription and translation occur at the same time because:
A
they have ribosomes
B
there is no nuclear envelope
C
mRNA is short
D
there is no RNA polymerase
Question 234 of 617
Official Ministerial Exam Question • High-Order Thinking
The number of possible codons is:
A
16
B
20
C
61
D
64
Question 235 of 617
Official Ministerial Exam Question • High-Order Thinking
The code is degenerate means:
A
it changes with time
B
several codons may code for one amino acid
C
a codon can code several amino acids
D
it differs among species
Question 236 of 617
Official Ministerial Exam Question • High-Order Thinking
Which is the start codon?
A
UAA
B
AUG
C
UGA
D
GUA
Question 237 of 617
Official Ministerial Exam Question • High-Order Thinking
Which is NOT a stop codon?
A
UAA
B
UAG
C
UGA
D
UGG
Question 238 of 617
Official Ministerial Exam Question • High-Order Thinking
The universality of the genetic code supports:
A
separate origins of species
B
common ancestry of living organisms
C
spontaneous generation
D
acquired characters
Question 239 of 617
Official Ministerial Exam Question • High-Order Thinking
A polypeptide of 21 amino acids needs at least … nucleotides in its mRNA:
A
21
B
42
C
63
D
69
Question 240 of 617
Official Ministerial Exam Question • High-Order Thinking
A gene of 150 nucleotide pairs codes for at most … amino acids:
A
25
B
50
C
75
D
150
Question 241 of 617
Official Ministerial Exam Question • High-Order Thinking
The DNA triplet 3′‑TAC‑5′ is transcribed into the mRNA codon:
A
UAC
B
AUG
C
ATG
D
TAC
Question 242 of 617
Official Ministerial Exam Question • High-Order Thinking
If a code were two-letter words, the number of codes would be:
A
4
B
8
C
16
D
64
Question 243 of 617
Official Ministerial Exam Question • High-Order Thinking
Translation begins when mRNA binds to the:
A
large ribosomal subunit
B
small ribosomal subunit
C
DNA polymerase
D
tRNA of lysine
Question 244 of 617
Official Ministerial Exam Question • High-Order Thinking
The first amino acid in a newly made polypeptide is usually:
A
lysine
B
glycine
C
methionine
D
alanine
Question 245 of 617
Official Ministerial Exam Question • High-Order Thinking
The peptide bond between amino acids is formed by:
A
releasing factor
B
peptidyl transferase
C
helicase
D
ligase
Question 246 of 617
Official Ministerial Exam Question • High-Order Thinking
The site where the second tRNA first enters the ribosome is the:
A
P site
B
A site
C
E site
D
promoter
Question 247 of 617
Official Ministerial Exam Question • High-Order Thinking
Translation stops when the ribosome meets a:
A
start codon
B
stop codon
C
promoter
D
poly‑A tail only
Question 248 of 617
Official Ministerial Exam Question • High-Order Thinking
A cluster of ribosomes on one mRNA is a:
A
nucleosome
B
polyribosome
C
plasmid
D
chromatin
Question 249 of 617
Official Ministerial Exam Question • High-Order Thinking
Heating DNA to 100 °C causes:
A
breaking of peptide bonds
B
separation of strands by breaking hydrogen bonds
C
loss of bases
D
formation of RNA
Question 250 of 617
Official Ministerial Exam Question • High-Order Thinking
Hybridisation can be used to:
A
estimate evolutionary relationships
B
make proteins
C
cut DNA
D
copy mRNA
Question 251 of 617
Official Ministerial Exam Question • High-Order Thinking
Restriction endonucleases are naturally produced by:
A
viruses
B
bacteria
C
plants
D
fungi only
Question 252 of 617
Official Ministerial Exam Question • High-Order Thinking
Bacterial DNA is protected from its own restriction enzymes by:
A
histones
B
methylation
C
the nuclear membrane
D
RNA
Question 253 of 617
Official Ministerial Exam Question • High-Order Thinking
Sticky ends are joined by:
A
helicase
B
DNA ligase
C
primase
D
reverse transcriptase
Question 254 of 617
Official Ministerial Exam Question • High-Order Thinking
The enzyme that makes DNA from an RNA template is:
A
DNA polymerase
B
RNA polymerase
C
reverse transcriptase
D
restriction enzyme
Question 255 of 617
Official Ministerial Exam Question • High-Order Thinking
Taq polymerase is used in PCR because it:
A
works at high temperature
B
cuts DNA
C
makes RNA
D
is found in humans
Question 256 of 617
Official Ministerial Exam Question • High-Order Thinking
The first recombinant DNA protein licensed for medical use was:
A
interferon
B
human insulin
C
growth hormone
D
haemoglobin
Question 257 of 617
Official Ministerial Exam Question • High-Order Thinking
The Human Genome Project was carried out in the period:
A
1950–1960
B
1975–1985
C
1990–2003
D
2010–2020
Question 258 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Physiological vs. Structural Support in Plants?
A
Physiological support is temporary and completely dependent on water uptake into vacuoles via osmosis, while structural support is permanent via deposition of cellulose, lignin, or suberin
B
Physiological support involves permanent deposition of lignin in stone cells
C
Both physiological and structural supports disappear immediately when the plant wilts
D
Structural support relies solely on turgor pressure of living parenchyma
Question 259 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Sliding Filament Theory of Muscle Contraction (Huxley)?
A
During sarcomere contraction, actin filaments slide over myosin filaments; the I-band and H-zone shorten, while the A-band length remains strictly constant
B
Both A-band and myosin filaments shrink by 50% in length
C
Z-lines move away from each other as the muscle contracts
D
Cross-bridges pull actin filaments outward away from the M-line
Question 260 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Hormonal Regulation of Blood Glucose (Insulin and Glucagon)?
A
Beta cells of the islets of Langerhans secrete insulin to lower blood glucose by stimulating cellular uptake and glycogen synthesis, while alpha cells secrete glucagon to raise blood glucose by glycogenolysis
B
Alpha cells secrete insulin to elevate blood glucose levels
C
Insulin stimulates the breakdown of liver glycogen into glucose
D
Glucagon is secreted by the adrenal cortex under stress
Question 261 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Parthenogenesis in Honeybees (Apis mellifera)?
A
The queen honeybee produces haploid drones (males, n) from unfertilized eggs via parthenogenesis, whereas diploid worker and queen females (2n) arise from fertilized eggs
B
Male drones arise from fertilized diploid zygotes (2n)
C
Female worker bees develop parthenogenetically without fertilization
D
Drones produce sperm cells by meiotic division
Question 262 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Plant Immunity: Role of Tyloses and Pre-existing Barriers?
A
Tyloses are balloon-like protrusions of xylem parenchyma cells that grow into xylem vessels through pits to block pathogen spread following vascular damage
B
Tyloses are biochemical antibodies synthesized by plant ribosomes
C
Tyloses accelerate the flow of infected sap to the leaves
D
Tyloses dissolve the fungal cell wall via chitinase enzymes
Question 263 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Chargaff's Rules of DNA Base Pairing?
A
In any double-stranded DNA molecule, the percentage of Adenine equals Thymine (%A = %T) and Guanine equals Cytosine (%G = %C), with total purines equaling pyrimidines (%A + %G = %T + %C = 50%)
B
Adenine bonds with Guanine via three hydrogen bonds
C
The percentage of %A + %T always equals 50% in all organisms
D
Uracil replaces Thymine in the double helix of nuclear DNA
Question 264 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Transcription and Translation during Protein Synthesis?
A
RNA polymerase synthesizes mRNA from the antisense DNA template strand in the 5' to 3' direction, and translation occurs on ribosomes where tRNA anticodons bind mRNA codons
B
DNA polymerase transcribes mRNA in the cytoplasm
C
Translation begins at the UAA stop codon
D
tRNA molecules contain codons identical to DNA triplets
Question 265 of 617
Official Ministerial Exam Question • High-Order Thinking
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Geological Dating and Index Fossils?
A
Index fossils must exhibit a wide geographic distribution and a short, well-defined chronological stratigraphic range to accurately correlate sedimentary rock layers
B
Index fossils must be restricted to a single local rock formation
C
Index fossils lived continuously throughout all geological eras
D
Index fossils are formed exclusively in intrusive igneous granite
Question 266 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 1: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 267 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 1: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 268 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 1: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 269 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 1: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 270 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 1: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 271 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 1: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 272 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 1: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 273 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 1: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 274 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 2: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 275 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 2: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 276 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 2: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 277 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 2: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 278 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 2: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 279 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 2: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 280 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 2: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 281 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 2: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 282 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 3: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 283 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 3: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 284 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 3: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 285 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 3: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 286 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 3: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 287 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 3: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 288 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 3: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 289 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 3: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 290 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 4: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 291 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 4: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 292 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 4: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 293 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 4: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 294 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 4: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 295 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 4: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 296 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 4: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 297 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 4: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 298 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 5: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 299 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 5: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 300 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 5: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 301 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 5: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 302 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 5: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 303 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 5: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 304 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 5: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 305 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 5: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 306 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 6: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 307 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 6: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 308 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 6: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 309 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 6: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 310 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 6: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 311 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 6: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 312 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 6: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 313 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 6: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 314 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 7: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 315 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 7: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 316 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 7: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 317 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 7: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 318 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 7: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 319 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 7: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 320 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 7: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 321 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 7: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 322 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 8: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 323 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 8: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 324 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 8: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 325 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 8: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 326 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 8: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 327 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 8: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 328 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 8: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 329 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 8: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 330 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 9: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 331 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 9: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 332 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 9: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 333 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 9: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 334 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 9: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 335 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 9: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 336 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 9: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 337 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 9: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 338 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 10: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 339 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 10: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 340 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 10: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 341 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 10: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 342 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 10: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 343 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 10: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 344 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 10: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 345 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 10: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 346 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 11: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 347 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 11: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 348 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 11: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 349 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 11: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 350 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 11: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 351 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 11: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 352 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 11: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 353 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 11: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 354 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 12: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 355 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 12: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 356 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 12: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 357 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 12: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 358 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 12: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 359 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 12: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 360 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 12: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 361 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 12: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 362 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 13: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 363 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 13: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 364 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 13: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 365 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 13: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 366 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 13: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 367 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 13: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 368 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 13: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 369 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 13: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 370 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 14: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 371 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 14: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 372 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 14: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 373 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 14: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 374 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 14: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 375 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 14: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 376 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 14: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 377 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 14: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 378 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 15: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 379 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 15: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 380 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 15: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 381 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 15: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 382 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 15: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 383 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 15: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 384 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 15: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 385 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 15: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 386 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 16: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 387 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 16: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 388 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 16: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 389 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 16: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 390 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 16: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 391 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 16: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 392 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 16: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 393 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 16: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 394 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 17: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 395 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 17: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 396 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 17: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 397 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 17: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 398 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 17: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 399 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 17: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 400 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 17: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 401 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 17: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 402 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 18: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 403 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 18: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 404 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 18: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 405 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 18: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 406 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 18: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 407 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 18: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 408 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 18: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 409 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 18: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 410 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 19: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 411 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 19: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 412 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 19: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 413 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 19: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 414 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 19: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 415 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 19: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 416 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 19: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 417 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 19: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 418 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 20: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 419 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 20: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 420 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 20: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 421 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 20: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 422 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 20: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 423 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 20: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 424 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 20: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 425 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 20: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 426 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 21: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 427 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 21: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 428 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 21: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 429 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 21: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 430 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 21: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 431 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 21: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 432 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 21: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 433 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 21: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 434 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 22: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 435 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 22: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 436 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 22: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 437 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 22: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 438 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 22: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 439 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 22: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 440 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 22: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 441 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 22: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 442 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 23: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 443 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 23: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 444 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 23: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 445 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 23: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 446 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 23: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 447 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 23: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 448 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 23: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 449 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 23: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 450 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 24: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 451 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 24: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 452 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 24: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 453 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 24: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 454 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 24: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 455 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 24: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 456 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 24: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 457 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 24: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 458 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 25: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 459 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 25: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 460 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 25: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 461 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 25: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 462 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 25: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 463 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 25: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 464 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 25: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 465 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 25: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 466 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 26: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 467 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 26: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 468 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 26: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 469 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 26: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 470 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 26: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 471 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 26: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 472 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 26: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 473 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 26: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 474 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 27: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 475 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 27: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 476 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 27: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 477 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 27: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 478 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 27: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 479 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 27: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 480 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 27: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 481 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 27: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 482 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 28: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 483 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 28: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 484 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 28: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 485 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 28: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 486 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 28: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 487 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 28: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 488 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 28: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 489 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 28: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 490 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 29: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 491 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 29: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 492 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 29: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 493 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 29: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 494 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 29: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 495 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 29: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 496 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 29: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 497 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 29: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 498 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 30: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 499 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 30: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 500 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 30: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 501 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 30: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 502 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 30: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 503 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 30: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 504 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 30: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 505 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 30: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 506 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 31: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 507 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 31: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 508 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 31: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 509 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 31: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 510 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 31: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 511 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 31: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 512 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 31: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 513 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 31: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 514 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 32: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 515 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 32: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 516 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 32: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 517 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 32: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 518 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 32: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 519 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 32: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 520 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 32: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 521 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 32: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 522 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 33: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 523 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 33: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 524 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 33: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 525 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 33: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 526 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 33: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 527 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 33: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 528 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 33: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 529 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 33: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 530 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 34: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 531 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 34: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 532 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 34: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 533 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 34: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 534 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 34: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 535 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 34: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 536 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 34: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 537 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 34: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 538 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 35: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 539 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 35: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 540 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 35: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 541 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 35: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 542 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 35: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 543 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 35: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 544 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 35: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 545 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 35: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 546 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 36: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 547 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 36: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 548 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 36: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 549 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 36: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 550 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 36: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 551 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 36: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 552 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 36: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 553 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 36: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 554 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 37: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 555 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 37: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 556 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 37: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 557 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 37: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 558 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 37: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 559 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 37: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 560 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 37: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 561 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 37: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 562 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 38: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 563 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 38: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 564 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 38: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 565 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 38: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 566 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 38: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 567 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 38: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 568 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 38: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 569 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 38: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 570 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 39: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 571 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 39: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 572 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 39: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 573 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 39: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 574 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 39: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 575 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 39: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 576 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 39: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 577 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 39: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 578 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 40: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 579 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 40: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 580 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 40: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 581 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 40: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 582 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 40: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 583 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 40: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 584 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 40: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 585 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 40: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 586 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 41: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 587 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 41: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 588 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 41: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 589 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 41: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 590 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 41: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 591 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 41: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 592 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 41: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 593 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 41: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 594 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 42: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 595 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 42: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 596 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 42: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 597 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 42: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 598 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 42: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 599 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 42: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 600 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 42: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 601 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 42: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 602 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 43: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 603 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 43: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 604 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 43: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 605 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 43: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 606 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 43: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 607 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 43: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 608 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 43: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 609 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 43: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
Question 610 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Biology Problem 44: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
A
360 Cytosine bases and 1,560 total hydrogen bonds
B
240 Cytosine bases and 1,200 hydrogen bonds
C
480 Cytosine bases and 1,800 hydrogen bonds
D
120 Cytosine bases and 960 hydrogen bonds
Question 611 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Genetics Question 44: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
A
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
B
150 tRNA molecules
C
151 tRNA molecules
D
75 tRNA molecules
Question 612 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Physiology Question 44: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
A
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
B
0 ATP molecules (relaxation is completely passive)
C
10 ATP molecules per fiber
D
1 ATP molecule shared across all 50 fibers
Question 613 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Immunology Question 44: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
A
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
B
Helper T-cells (CD4+ Th) exclusively
C
Plasma B-cells secreting IgG
D
Mast cells releasing histamine
Question 614 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Endocrinology Question 44: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
A
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
B
Simple endemic goiter due to iodine deficiency
C
Myxedema resulting from severe hypothyroidism in adults
D
Cushing's syndrome from elevated cortisol
Question 615 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Ecology Question 44: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
A
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
B
Broad thin leaves with dense stomata on both surfaces
C
Absence of xylem vessels and thin cellulose walls
D
Rapid continuous transpiration during midday heat
Question 616 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Geology Question 44: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
A
Normal fault resulting from crustal extensional (tensional) forces
B
Reverse fault caused by lateral compressional stress
C
Thrust fault with an inclination angle less than 45 degrees
D
Strike-slip fault with purely horizontal displacement
Question 617 of 617
Official Ministerial Exam Question • High-Order Thinking
STEM Molecular Genetics Question 44: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
A
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
B
They permanently destroy DNA ligase activity
C
They prevent plasmids from entering bacterial cells
D
They mutate bacterial resistance genes permanently
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📋 Full 617-Question Review & Official Explanations
Side-by-side comparison of your answers and official ministerial solutions with detailed scientific explanations.
Question 1
Unanswered
The stop codons that signal termination of translation on an mRNA molecule include:
(A)
AUG, UAA, UGA
(B)
UAA, UAG, UGA
(C)
UAC, UGG, UAA
(D)
GUA, CAU, UAG
Official Scientific Justification: UAA, UAG, and UGA are the three universal termination codons recognized by Release Factor.
Question 2
Unanswered
In a young herbaceous stem, the main force that keeps the plant upright is:
(A)
lignin in the xylem
(B)
turgor pressure of the cells
(C)
the cork layer
(D)
the root system only
Official Scientific Justification: Water-filled cells press against their walls and make the soft tissues firm.
Question 3
Unanswered
The waterproof substance deposited on the outer walls of epidermal cells is:
(A)
lignin
(B)
suberin
(C)
cutin
(D)
cellulose
Official Scientific Justification: Cutin forms the cuticle and reduces water loss; suberin is in cork.
Question 4
Unanswered
Suberin is found in the walls of:
(A)
cork cells
(B)
guard cells
(C)
collenchyma
(D)
root hairs
Official Scientific Justification: Cork cells are impermeable because of suberin.
Question 5
Unanswered
Collenchyma cells are thickened with:
(A)
lignin
(B)
cellulose
(C)
cutin
(D)
suberin
Official Scientific Justification: They have unevenly thickened cellulose walls and stay alive, so they support growing parts.
Question 6
Unanswered
Which tissue forms the tough fibres of a celery stalk?
(A)
parenchyma
(B)
epidermis
(C)
sclerenchyma
(D)
phloem sieve tubes
Official Scientific Justification: Sclerenchyma has lignified walls and gives rigid support.
Question 7
Unanswered
A plant that has lost water becomes limp because:
(A)
its lignin dissolves
(B)
its cells lose turgor
(C)
its cellulose is digested
(D)
its cuticle is removed
Official Scientific Justification: Loss of water reduces the pressure inside the cells and they become flaccid.
Question 8
Unanswered
The type of skeleton found in an earthworm is:
(A)
exoskeleton
(B)
endoskeleton
(C)
hydrostatic skeleton
(D)
cartilage only
Official Scientific Justification: Fluid in the body cavity acted on by muscles gives support and movement.
Question 9
Unanswered
The total number of bones in the adult human skeleton is:
(A)
33
(B)
206
(C)
620
(D)
300
Official Scientific Justification: 206 bones; 33 is the number of vertebrae; 620 is the approximate number of muscles.
Question 10
Unanswered
The axial skeleton includes:
(A)
the skull, vertebral column and thoracic cage
(B)
the pectoral girdle and arm bones
(C)
the pelvic girdle and leg bones
(D)
the girdles only
Official Scientific Justification: Limbs and girdles form the appendicular skeleton.
Question 11
Unanswered
The number of cervical vertebrae in man is:
(A)
5
(B)
7
(C)
12
(D)
4
Official Scientific Justification: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal.
Question 12
Unanswered
The largest vertebrae are found in the:
(A)
cervical region
(B)
thoracic region
(C)
lumbar region
(D)
coccygeal region
Official Scientific Justification: They carry the weight of the upper body.
Question 13
Unanswered
Which vertebrae are fused together?
(A)
cervical and thoracic
(B)
thoracic and lumbar
(C)
lumbar and sacral only
(D)
sacral and coccygeal
Official Scientific Justification: Five sacral form the sacrum; four coccygeal form the coccyx.
Question 14
Unanswered
The spinal cord passes through the:
(A)
neural canal
(B)
centrum
(C)
transverse process
(D)
neural spine
Official Scientific Justification: The neural arch and centrum enclose the neural canal.
Question 15
Unanswered
The large opening at the base of the skull is the:
(A)
foramen magnum
(B)
acetabulum
(C)
glenoid cavity
(D)
pubic symphysis
Official Scientific Justification: The spinal cord joins the brain through it.
Question 16
Unanswered
The number of bones forming the facial part of the skull is:
(A)
8
(B)
12
(C)
14
(D)
22
Official Scientific Justification: The cranial part has 8 bones and the facial part has 14.
Question 17
Unanswered
The floating ribs are:
(A)
the first two pairs
(B)
the last two pairs
(C)
the middle two pairs
(D)
all 12 pairs
Official Scientific Justification: The last two pairs are short and do not reach the sternum.
Question 18
Unanswered
The bone that fits into the glenoid cavity is the head of the:
(A)
femur
(B)
humerus
(C)
radius
(D)
clavicle
Official Scientific Justification: This forms the shoulder joint.
Question 19
Unanswered
The forearm is supported by:
(A)
humerus only
(B)
tibia and fibula
(C)
radius and ulna
(D)
scapula and clavicle
Official Scientific Justification: Radius and ulna; the radius rotates around the fixed ulna.
Question 20
Unanswered
How many phalanges does the thumb have?
(A)
1
(B)
2
(C)
3
(D)
4
Official Scientific Justification: The thumb has two; the other fingers have three each.
Question 21
Unanswered
The wrist is formed of:
(A)
5 metacarpals
(B)
8 carpals
(C)
7 tarsals
(D)
14 phalanges
Official Scientific Justification: The ankle has 7 tarsals; the wrist has 8 carpals.
Question 22
Unanswered
The acetabulum is the cavity of the:
(A)
pectoral girdle
(B)
skull
(C)
pelvic girdle
(D)
elbow
Official Scientific Justification: It is formed where ilium, ischium and pubis meet and receives the head of the femur.
Question 23
Unanswered
The bone in front of the knee joint is the:
(A)
patella
(B)
fibula
(C)
tarsal
(D)
scapula
Official Scientific Justification: The knee-cap.
Question 24
Unanswered
Cartilage obtains its food and oxygen by:
(A)
blood vessels inside it
(B)
diffusion from nearby tissues
(C)
phagocytosis
(D)
active transport from muscle
Official Scientific Justification: Cartilage has no blood vessels.
Question 25
Unanswered
The joints between the skull bones are:
(A)
fibrous
(B)
cartilaginous
(C)
synovial ball-and-socket
(D)
hinge
Official Scientific Justification: Fibrous joints allow no movement.
Question 26
Unanswered
Which is a ball-and-socket joint?
(A)
elbow
(B)
knee
(C)
hip
(D)
between vertebrae
Official Scientific Justification: The shoulder and hip allow movement in many directions.
Question 27
Unanswered
The fluid that lubricates synovial joints is:
(A)
synovial fluid
(B)
lymph
(C)
bile
(D)
cerebrospinal fluid
Official Scientific Justification: It reduces friction and absorbs shocks.
Question 28
Unanswered
Ligaments connect:
(A)
muscle to bone
(B)
bone to bone
(C)
muscle to muscle
(D)
skin to muscle
Official Scientific Justification: They stabilise joints and determine direction of movement.
Question 29
Unanswered
The Achilles tendon connects the:
(A)
biceps to radius
(B)
gastrocnemius muscle to the heel bone
(C)
quadriceps to the patella
(D)
femur to tibia
Official Scientific Justification: It lets the calf muscle raise the heel.
Question 30
Unanswered
The leaflets of Mimosa fold when touched. This movement is called:
(A)
tropism
(B)
cytoplasmic streaming
(C)
touch movement
(D)
pulling movement
Official Scientific Justification: A response to contact, caused by loss of turgor in the leaf base.
Question 31
Unanswered
A tendril twines round a support because:
(A)
the side touching the support grows faster
(B)
the side away from the support grows faster
(C)
the tendril cells die on one side
(D)
the whole tendril contracts
Official Scientific Justification: Slower growth on the contact side and faster growth on the far side bend the tendril.
Question 32
Unanswered
Corms and bulbs are kept at a suitable depth in the soil by:
(A)
tendrils
(B)
pulling (contractile) roots
(C)
thorns
(D)
rhizoids
Official Scientific Justification: Contraction of these roots pulls the storage organ down.
Question 33
Unanswered
Cytoplasmic streaming is easily observed in the leaf cells of:
(A)
Mimosa
(B)
pea
(C)
Elodea
(D)
onion bulb
Official Scientific Justification: Chloroplasts moving with the cytoplasm are seen under the microscope.
Question 34
Unanswered
The systems that coordinate to produce movement in man are:
(A)
skeletal, nervous and muscular
(B)
skeletal, digestive and circulatory
(C)
muscular, respiratory and nervous
(D)
nervous, endocrine and excretory
Official Scientific Justification: The skeleton gives levers, muscles contract, and nerves give the order.
Question 35
Unanswered
Each muscle fibre is:
(A)
uninucleate
(B)
multinucleated
(C)
without a membrane
(D)
without myofibrils
Official Scientific Justification: A skeletal muscle fibre is a long cell with many nuclei.
Question 36
Unanswered
The cell membrane of a muscle fibre is called:
(A)
sarcoplasm
(B)
sarcolemma
(C)
perimysium
(D)
myofibril
Official Scientific Justification: Sarcoplasm is its cytoplasm; perimysium surrounds a bundle.
Question 37
Unanswered
The thin filaments of a myofibril are made of:
(A)
myosin
(B)
actin
(C)
keratin
(D)
collagen
Official Scientific Justification: Actin forms the thin filaments (I-band) and myosin the thick filaments (A-band).
Question 38
Unanswered
The distance between two successive Z-lines is a:
(A)
myofibril
(B)
sarcomere
(C)
fascicle
(D)
H-zone
Official Scientific Justification: It is the contractile unit.
Question 39
Unanswered
The transmitter that carries the impulse across the neuromuscular junction is:
(A)
cholinesterase
(B)
acetylcholine
(C)
adrenaline
(D)
thyroxine
Official Scientific Justification: Cholinesterase is the enzyme that destroys it.
Question 40
Unanswered
Acetylcholine is broken down by cholinesterase into:
(A)
glucose and fructose
(B)
choline and acetic acid
(C)
lactic acid and CO2
(D)
amino acids
Official Scientific Justification: This ends the stimulation and allows repolarisation.
Question 41
Unanswered
When a muscle contracts, which band does NOT change in length?
(A)
I-band
(B)
H-zone
(C)
A-band
(D)
distance between Z-lines
Official Scientific Justification: The myosin filaments keep the same length; the actin filaments slide.
Question 42
Unanswered
The immediate source of energy for muscle contraction is:
(A)
glycogen
(B)
glucose
(C)
ATP
(D)
lactic acid
Official Scientific Justification: ATP is used to attach and detach the cross-bridges.
Question 43
Unanswered
Muscle fatigue is caused by accumulation of:
(A)
carbon dioxide
(B)
lactic acid
(C)
acetic acid
(D)
urea
Official Scientific Justification: Anaerobic breakdown of glycogen produces lactic acid.
Question 44
Unanswered
Endocrine glands release their secretions:
(A)
through ducts into the intestine
(B)
through ducts to the outside
(C)
directly into the blood
(D)
into the lymph nodes only
Official Scientific Justification: They are ductless glands.
Question 45
Unanswered
Who discovered the first animal hormone (secretin) and coined the word hormone?
(A)
Jensen
(B)
Starling
(C)
Huxley
(D)
Banting
Official Scientific Justification: Starling (1905) showed that the duodenal lining releases a chemical that stimulates the pancreas.
Question 46
Unanswered
In Starling's experiment the pancreas still secreted juice after its nerves were cut. This proved that:
(A)
the pancreas secretes without any stimulus
(B)
a non-nervous (chemical) stimulus exists
(C)
nerves are useless
(D)
the stomach controls the pancreas
Official Scientific Justification: A chemical carried by blood acted as messenger.
Question 47
Unanswered
The word "hormone" means:
(A)
to digest
(B)
to build
(C)
to activate or excite
(D)
to protect
Official Scientific Justification: It is a Greek word meaning "activators".
Question 48
Unanswered
Jensen explained phototropism using:
(A)
thyroxine
(B)
auxins
(C)
insulin
(D)
oxytocin
Official Scientific Justification: Auxins such as indole acetic acid transmit the effect of light from the tip to the region of curvature.
Question 49
Unanswered
Plant hormones (auxins) are produced by:
(A)
special glands
(B)
tips of coleoptiles and buds
(C)
roots only
(D)
the cuticle
Official Scientific Justification: Plants have no special glands.
Question 50
Unanswered
Hormones are secreted in:
(A)
grams
(B)
milligrams
(C)
micrograms (very small amounts)
(D)
kilograms
Official Scientific Justification: A microgram is 1/1000 milligram.
Question 51
Unanswered
Which hormone is a steroid?
(A)
insulin
(B)
thyroxine
(C)
progesterone
(D)
glucagon
Official Scientific Justification: Sex hormones and adrenal cortex hormones are steroids.
Question 52
Unanswered
Which of the following is a mixed gland?
(A)
thyroid
(B)
pancreas
(C)
pituitary
(D)
adrenal
Official Scientific Justification: It has an exocrine part (juice) and endocrine islets.
Question 53
Unanswered
The pituitary gland is joined to the brain by the:
(A)
isthmus
(B)
infundibulum
(C)
cerebellum
(D)
corpus callosum
Official Scientific Justification: The infundibulum connects it with the hypothalamus.
Question 54
Unanswered
Which pituitary lobe belongs to the adenohypophysis?
(A)
posterior lobe
(B)
anterior lobe
(C)
infundibulum
(D)
none of them
Official Scientific Justification: The adenohypophysis comprises the anterior and middle lobes.
Question 55
Unanswered
Excess growth hormone in a child causes:
(A)
dwarfism
(B)
acromegaly
(C)
gigantism
(D)
cretinism
Official Scientific Justification: In adults the same excess causes acromegaly.
Question 56
Unanswered
Acromegaly is characterised by:
(A)
very tall stature with normal proportions
(B)
enlarged hands, feet and face bones in an adult
(C)
dry skin and weight gain
(D)
protruding eyeballs
Official Scientific Justification: Bones of the extremities grow in thickness after normal growth has stopped.
Question 57
Unanswered
The hormone that stimulates milk secretion from the mammary glands is:
(A)
oxytocin
(B)
prolactin
(C)
progesterone
(D)
ADH
Official Scientific Justification: Oxytocin only causes milk ejection.
Question 58
Unanswered
Which hormone stimulates the adrenal cortex?
(A)
TSH
(B)
ACTH
(C)
FSH
(D)
LH
Official Scientific Justification: Adrenocorticotrophic hormone.
Question 59
Unanswered
The hormones of the posterior lobe are made in the:
(A)
liver
(B)
hypothalamus
(C)
thyroid
(D)
adrenal medulla
Official Scientific Justification: They are made by neurosecretory cells of the hypothalamus and stored in the posterior lobe.
Question 60
Unanswered
ADH acts on:
(A)
the liver
(B)
the kidney tubules
(C)
the pancreas
(D)
the thyroid
Official Scientific Justification: It increases water reabsorption and reduces urine volume.
Question 61
Unanswered
The hormone used by doctors to accelerate delivery is:
(A)
oxytocin
(B)
prolactin
(C)
FSH
(D)
thyroxine
Official Scientific Justification: It strongly contracts the uterine muscles.
Question 62
Unanswered
FSH in the male stimulates:
(A)
the interstitial cells to make testosterone
(B)
the seminiferous tubules to produce sperms
(C)
the prostate gland
(D)
the adrenal gland
Official Scientific Justification: LH is the one acting on the interstitial cells.
Question 63
Unanswered
The thyroid gland lies:
(A)
behind the stomach
(B)
above the kidneys
(C)
in the neck in front of the trachea
(D)
under the brain
Official Scientific Justification: Two lobes joined by an isthmus.
Question 64
Unanswered
The element essential for the manufacture of thyroxine is:
(A)
calcium
(B)
iron
(C)
iodine
(D)
sodium
Official Scientific Justification: Lack of iodine causes simple goitre.
Question 65
Unanswered
Cretinism results from:
(A)
hyposecretion of thyroxine in childhood
(B)
hypersecretion of thyroxine in an adult
(C)
hypersecretion of GH in childhood
(D)
lack of insulin
Official Scientific Justification: Severe thyroxine deficiency in a child retards physical and mental growth.
Question 66
Unanswered
Dry skin, hair loss, obesity and intolerance to cold in an adult indicate:
(A)
exophthalmic goitre
(B)
myxoedema
(C)
acromegaly
(D)
diabetes mellitus
Official Scientific Justification: Severe hypothyroidism of adults.
Question 67
Unanswered
Protruding eyeballs, weight loss and rapid heartbeat are symptoms of:
(A)
simple goitre
(B)
cretinism
(C)
exophthalmic goitre
(D)
tetany
Official Scientific Justification: Hypersecretion of thyroxine.
Question 68
Unanswered
The hormone that lowers blood calcium is:
(A)
parathormone
(B)
calcitonin
(C)
aldosterone
(D)
insulin
Official Scientific Justification: Calcitonin from the thyroid antagonises parathormone.
Question 69
Unanswered
Hypersecretion of parathormone leads to:
(A)
muscle spasms
(B)
fragile bones
(C)
goitre
(D)
dwarfism
Official Scientific Justification: Calcium is withdrawn from the bones, so they become fragile.
Question 70
Unanswered
Painful muscular convulsions result from:
(A)
hypoparathyroidism
(B)
hyperparathyroidism
(C)
hyperthyroidism
(D)
hypersecretion of GH
Official Scientific Justification: Low blood calcium makes nerves and muscles over-excitable.
Question 71
Unanswered
Aldosterone mainly regulates:
(A)
blood glucose
(B)
sodium and potassium balance
(C)
calcium
(D)
body growth
Official Scientific Justification: It increases sodium reabsorption and potassium excretion.
Question 72
Unanswered
The hormone secreted in emergency (fight and flight) is:
(A)
adrenaline
(B)
cortisone
(C)
insulin
(D)
progesterone
Official Scientific Justification: From the adrenal medulla.
Question 73
Unanswered
Adrenaline increases blood glucose by:
(A)
converting glucose to glycogen
(B)
breaking down liver glycogen
(C)
stopping glucose uptake by cells
(D)
inhibiting insulin receptors only
Official Scientific Justification: It also increases heart rate and blood pressure.
Question 74
Unanswered
Cortisone belongs to the group of:
(A)
mineralocorticoids
(B)
glucocorticoids
(C)
sex hormones
(D)
amino-acid hormones
Official Scientific Justification: They regulate carbohydrate metabolism.
Question 75
Unanswered
A tumour of the adrenal cortex in a woman may cause:
(A)
feminisation
(B)
masculinisation
(C)
goitre
(D)
dwarfism
Official Scientific Justification: Excess male-type sex hormones.
Question 76
Unanswered
Insulin is secreted by:
(A)
alpha cells
(B)
beta cells of the islets of Langerhans
(C)
pancreatic acini
(D)
the adrenal cortex
Official Scientific Justification: Beta cells are the majority; alpha cells secrete glucagon.
Question 77
Unanswered
The normal blood glucose level is about:
(A)
8-12 mg/100 cm3
(B)
80-120 mg/100 cm3
(C)
300-400 mg/100 cm3
(D)
800-1200 mg/100 cm3
Official Scientific Justification: The two pancreatic hormones keep it constant in this range.
Question 78
Unanswered
Glucagon increases blood glucose by converting glycogen into glucose in the:
(A)
muscles
(B)
liver only
(C)
kidney
(D)
intestine
Official Scientific Justification: Only the liver releases glucose into the blood.
Question 79
Unanswered
Which sugar enters cells without needing insulin, according to the book?
(A)
glucose
(B)
galactose
(C)
fructose
(D)
mannose
Official Scientific Justification: Insulin helps transport all monosaccharides except fructose.
Question 80
Unanswered
A diabetic patient has continuous thirst because:
(A)
the kidney stops working
(B)
glucose in the urine draws water out, causing large urine volumes
(C)
the sweat glands are over-active
(D)
insulin is stored in the kidney
Official Scientific Justification: Loss of water in urine causes thirst.
Question 81
Unanswered
The male sex hormones are secreted by the:
(A)
Sertoli cells
(B)
interstitial cells of the testes
(C)
prostate gland
(D)
seminal vesicles
Official Scientific Justification: Testosterone comes from interstitial (Leydig) cells.
Question 82
Unanswered
The hormone that relaxes the pubic symphysis at the end of pregnancy is:
(A)
progesterone
(B)
oestrogen
(C)
relaxin
(D)
oxytocin
Official Scientific Justification: Secreted by the placenta and uterus.
Question 83
Unanswered
Cholecystokinin causes:
(A)
gastric juice secretion
(B)
contraction of the gall bladder
(C)
secretion of insulin
(D)
release of bile salts into blood
Official Scientific Justification: It also stimulates pancreatic enzymes.
Question 84
Unanswered
Which hormone is secreted by the stomach wall?
(A)
secretin
(B)
gastrin
(C)
CCK
(D)
insulin
Official Scientific Justification: Gastrin stimulates gastric juice secretion.
Question 85
Unanswered
Compared with the nervous system, hormonal control is:
(A)
faster and shorter in effect
(B)
slower and longer in effect
(C)
faster and longer in effect
(D)
slower and shorter in effect
Official Scientific Justification: Hormones travel by the blood, so are slower but longer lasting.
Question 86
Unanswered
Reproduction is essential for:
(A)
the life of each individual
(B)
the continuity of the species
(C)
respiration
(D)
digestion
Official Scientific Justification: An individual can live without reproducing, but the species would become extinct.
Question 87
Unanswered
Which organisms usually produce the largest number of offspring?
(A)
mammals
(B)
birds
(C)
parasites and aquatic animals
(D)
primates
Official Scientific Justification: Heavy losses of young must be compensated for.
Question 88
Unanswered
Asexual reproduction depends on:
(A)
meiosis
(B)
mitosis
(C)
fertilisation
(D)
crossing over
Official Scientific Justification: Mitosis gives genetically identical cells.
Question 89
Unanswered
Reproduction in Amoeba is by:
(A)
budding
(B)
binary fission
(C)
spores
(D)
conjugation
Official Scientific Justification: The nucleus divides by mitosis, then the cell divides.
Question 90
Unanswered
In yeast, the new individual arises as a:
(A)
spore
(B)
bud
(C)
gamete
(D)
zygote
Official Scientific Justification: A lateral projection receiving a daughter nucleus.
Question 91
Unanswered
The bud of Hydra arises by division of:
(A)
interstitial cells
(B)
nerve cells
(C)
stinging cells
(D)
gland cells
Official Scientific Justification: These cells divide and differentiate.
Question 92
Unanswered
An animal that regenerates a whole body from a piece is:
(A)
frog
(B)
Planaria
(C)
rabbit
(D)
bird
Official Scientific Justification: Planaria and Hydra can regenerate from pieces.
Question 93
Unanswered
Which organism reproduces by spores?
(A)
Hydra
(B)
bread mould
(C)
Planaria
(D)
Amoeba
Official Scientific Justification: Mushrooms and bread mould reproduce by spores.
Question 94
Unanswered
Drones of the honey bee are:
(A)
diploid, from fertilised eggs
(B)
haploid, from unfertilised eggs
(C)
triploid
(D)
female
Official Scientific Justification: This is parthenogenesis.
Question 95
Unanswered
Tissue culture proves that any plant somatic cell:
(A)
lacks genes
(B)
carries the complete genetic information
(C)
cannot divide
(D)
is haploid
Official Scientific Justification: A whole plant can develop from a single cell.
Question 96
Unanswered
The liquid that supplied nutrients and hormones in the carrot tissue culture experiment was:
(A)
cow milk
(B)
coconut milk
(C)
blood plasma
(D)
honey solution
Official Scientific Justification: Coconut milk contains plant hormones and nutrients.
Question 97
Unanswered
Conjugation occurs in:
(A)
Spirogyra
(B)
Amoeba
(C)
Hydra
(D)
Planaria
Official Scientific Justification: Spirogyra has scalariform and lateral conjugation.
Question 98
Unanswered
The cells of a Spirogyra filament are:
(A)
diploid
(B)
haploid
(C)
triploid
(D)
tetraploid
Official Scientific Justification: Only the zygote is diploid; it undergoes meiosis on germination.
Question 99
Unanswered
The zygote of Spirogyra with a thick wall is the:
(A)
oocyst
(B)
zygospore
(C)
ookinete
(D)
blastocyst
Official Scientific Justification: It rests until conditions improve.
Question 100
Unanswered
Fertilisation is external in:
(A)
reptiles
(B)
birds
(C)
bony fish and frogs
(D)
mammals
Official Scientific Justification: They shed gametes in water.
Question 101
Unanswered
The infective stage that the mosquito injects into man is the:
(A)
merozoite
(B)
sporozoite
(C)
gametocyte
(D)
ookinete
Official Scientific Justification: Sporozoites go to the liver.
Question 102
Unanswered
The sexual generation of Plasmodium takes place in:
(A)
human liver
(B)
human red blood cells
(C)
female Anopheles
(D)
male Anopheles
Official Scientific Justification: Gametes fuse in the mosquito's stomach.
Question 103
Unanswered
Malaria fever appears when:
(A)
sporozoites enter the blood
(B)
merozoites burst out of red blood cells
(C)
gametocytes form
(D)
the oocyst forms
Official Scientific Justification: Toxins are released with the merozoites.
Question 104
Unanswered
In ferns, the spores are produced by meiosis in the:
(A)
gametophyte
(B)
sporophyte
(C)
archegonium
(D)
antheridium
Official Scientific Justification: Spore mother cells (2N) in the sporangia divide by meiosis.
Question 105
Unanswered
The male sex organs of a fern gametophyte are the:
(A)
archegonia
(B)
antheridia
(C)
sori
(D)
rhizoids
Official Scientific Justification: They produce ciliated sperms.
Question 106
Unanswered
The male part of a flower is the:
(A)
gynoecium
(B)
androecium
(C)
calyx
(D)
corolla
Official Scientific Justification: A set of stamens.
Question 107
Unanswered
The part of the carpel that receives pollen is the:
(A)
ovary
(B)
style
(C)
stigma
(D)
micropyle
Official Scientific Justification: Sticky or feathery.
Question 108
Unanswered
The calyx is formed of:
(A)
petals
(B)
sepals
(C)
stamens
(D)
carpels
Official Scientific Justification: Green sepals protect the bud.
Question 109
Unanswered
Each pollen mother cell gives:
(A)
2 pollen grains
(B)
4 pollen grains
(C)
8 pollen grains
(D)
1 pollen grain
Official Scientific Justification: Meiosis produces four microspores.
Question 110
Unanswered
A mature pollen grain before germination contains:
(A)
one nucleus
(B)
tube nucleus and generative nucleus
(C)
three nuclei
(D)
four nuclei
Official Scientific Justification: The microspore nucleus divides mitotically into two.
Question 111
Unanswered
The mature embryo sac contains how many nuclei?
(A)
4
(B)
6
(C)
8
(D)
16
Official Scientific Justification: Three mitotic divisions of the surviving megaspore give 8.
Question 112
Unanswered
The ploidy of the endosperm nucleus is:
(A)
N
(B)
2N
(C)
3N
(D)
4N
Official Scientific Justification: One male nucleus (N) + two polar nuclei (N + N).
Question 113
Unanswered
The pollen tube enters the ovule through the:
(A)
funicle
(B)
micropyle
(C)
stigma
(D)
style
Official Scientific Justification: The tiny opening between the integuments.
Question 114
Unanswered
The seed coat (testa) develops from the:
(A)
ovary wall
(B)
integuments
(C)
nucellus
(D)
endosperm
Official Scientific Justification: The ovary wall becomes the pericarp.
Question 115
Unanswered
Which seed is non-endospermic?
(A)
wheat
(B)
maize
(C)
bean
(D)
castor
Official Scientific Justification: Food is stored in the cotyledons.
Question 116
Unanswered
The apple is a false fruit because it develops from the:
(A)
ovary only
(B)
receptacle together with the ovary
(C)
petals
(D)
stigma
Official Scientific Justification: A flower part other than the ovary enlarges.
Question 117
Unanswered
Seedless banana is formed by:
(A)
parthenogenesis
(B)
parthenocarpy
(C)
budding
(D)
tissue culture
Official Scientific Justification: A fruit develops without fertilisation.
Question 118
Unanswered
The testes lie in the scrotum because:
(A)
the abdomen is full
(B)
a lower temperature suits spermatogenesis
(C)
they secrete hormones there only
(D)
the scrotum is warmer
Official Scientific Justification: A temperature lower than that of the body is needed.
Question 119
Unanswered
Testosterone is secreted by the:
(A)
Sertoli cells
(B)
interstitial cells
(C)
epididymis
(D)
seminal vesicles
Official Scientific Justification: Located between the seminiferous tubules.
Question 120
Unanswered
The secretion of the seminal vesicles contains:
(A)
fructose
(B)
lactose
(C)
insulin
(D)
FSH
Official Scientific Justification: It nourishes sperms.
Question 121
Unanswered
In spermatogenesis, the cell that undergoes meiosis I is the:
(A)
spermatogonium
(B)
primary spermatocyte
(C)
secondary spermatocyte
(D)
spermatid
Official Scientific Justification: It produces two secondary spermatocytes.
Question 122
Unanswered
The structure that supplies the sperm with energy is the:
(A)
acrosome
(B)
mitochondria in the midpiece
(C)
centrioles
(D)
nucleus
Official Scientific Justification: ATP powers the tail.
Question 123
Unanswered
The acrosome secretes:
(A)
amylase
(B)
hyaluronidase
(C)
pepsin
(D)
lipase
Official Scientific Justification: It dissolves part of the ovum coat.
Question 124
Unanswered
One primary oocyte forms:
(A)
4 ova
(B)
2 ova
(C)
1 ovum and polar bodies
(D)
3 ova
Official Scientific Justification: Unequal division concentrates the cytoplasm in one cell.
Question 125
Unanswered
Oogonia are formed during the:
(A)
puberty
(B)
embryonic stage
(C)
pregnancy
(D)
menopause
Official Scientific Justification: Multiplication and growth phases occur before birth.
Question 126
Unanswered
In a 28-day cycle ovulation occurs on about day:
(A)
1
(B)
7
(C)
14
(D)
21
Official Scientific Justification: Triggered by the LH surge.
Question 127
Unanswered
Ovulation is caused by:
(A)
FSH
(B)
LH
(C)
progesterone
(D)
prolactin
Official Scientific Justification: LH makes the Graafian follicle rupture.
Question 128
Unanswered
The corpus luteum develops from the:
(A)
endometrium
(B)
Graafian follicle
(C)
placenta
(D)
oviduct
Official Scientific Justification: After ovulation the follicle becomes the yellow body.
Question 129
Unanswered
Fertilisation normally occurs in the:
(A)
uterus
(B)
vagina
(C)
upper third of the Fallopian tube
(D)
ovary
Official Scientific Justification: Ovum and sperms meet there.
Question 130
Unanswered
The embryo implants in the uterus at the end of:
(A)
the first day
(B)
the first week
(C)
the third month
(D)
the ninth month
Official Scientific Justification: As a blastocyst.
Question 131
Unanswered
The amnion contains fluid that:
(A)
feeds the embryo
(B)
protects the embryo from shocks and dryness
(C)
makes hormones
(D)
removes carbon dioxide
Official Scientific Justification: The outer membrane is the chorion.
Question 132
Unanswered
After the fourth month progesterone is mainly secreted by the:
(A)
corpus luteum
(B)
placenta
(C)
pituitary
(D)
adrenal
Official Scientific Justification: The corpus luteum degenerates.
Question 133
Unanswered
The contraceptive pill prevents pregnancy by:
(A)
blocking the oviducts
(B)
inhibiting ovulation
(C)
killing sperms in the testes
(D)
preventing implantation only
Official Scientific Justification: Oestrogen and progesterone inhibit FSH and LH.
Question 134
Unanswered
Identical twins result from:
(A)
two ova and two sperms
(B)
one ovum and one sperm, then splitting
(C)
one ovum and two sperms
(D)
two ova and one sperm
Official Scientific Justification: The early embryo divides into two.
Question 135
Unanswered
In vitro fertilisation means fertilisation:
(A)
in the oviduct
(B)
in the uterus
(C)
outside the body in a dish
(D)
in the ovary
Official Scientific Justification: The embryo is then placed in the uterus.
Question 136
Unanswered
Dolly the sheep was produced from:
(A)
a fertilised egg
(B)
a nucleus from an adult mammary gland cell placed in an enucleated egg
(C)
a drone
(D)
parthenocarpy
Official Scientific Justification: Cloning by nuclear transfer.
Question 137
Unanswered
X and Y sperms can be separated by:
(A)
distillation
(B)
centrifugation or electrophoresis
(C)
filtration
(D)
chromatography on paper only
Official Scientific Justification: Used for sex control in cattle.
Question 138
Unanswered
Immunity is best defined as the ability of an organism to:
(A)
produce hormones
(B)
resist pathogens through its immune system
(C)
digest food rapidly
(D)
avoid all contact with microbes
Official Scientific Justification: Immunity means resisting pathogens, either by keeping them out or by destroying them.
Question 139
Unanswered
Which pair correctly names the two cooperating immune systems of animals?
(A)
Structural and biochemical
(B)
Primary and secondary
(C)
Innate and acquired
(D)
Humoral and hormonal
Official Scientific Justification: Structural/biochemical describes plants; primary/secondary describes responses or lymphoid organs.
Question 140
Unanswered
A waxy layer of cutin on leaves helps defence because it:
(A)
absorbs water for fungi
(B)
prevents water settling, so microbes cannot grow easily
(C)
kills bacteria with toxins
(D)
is made of lignin
Official Scientific Justification: A dry surface gives fungi and bacteria no suitable film of moisture.
Question 141
Unanswered
Cork cell walls are thickened with:
(A)
cellulose only
(B)
chitin
(C)
suberin
(D)
pectin only
Official Scientific Justification: Suberin makes cork waterproof and protective.
Question 142
Unanswered
Tyloses are outgrowths of:
(A)
sieve tubes into phloem
(B)
parenchyma protoplasts into xylem vessels
(C)
epidermal cells into the cuticle
(D)
root hairs into the soil
Official Scientific Justification: Living parenchyma cells bulge through pits into vessels and tracheids and block them.
Question 143
Unanswered
Which of these is a biochemical (not structural) defence in plants?
(A)
Gum deposition
(B)
Tylosis formation
(C)
Phenol production
(D)
Cork formation
Official Scientific Justification: Phenols are toxic chemicals; the others are physical barriers.
Question 144
Unanswered
Canavanine is an example of:
(A)
a plant hormone
(B)
a non-protein amino acid toxic to pathogens
(C)
a structural protein
(D)
a detoxifying enzyme
Official Scientific Justification: Non-protein amino acids do not enter plant proteins but poison pathogens.
Question 145
Unanswered
Deliberate death of tissue around an infection, so the pathogen cannot spread, is called:
(A)
tylosis
(B)
hypersensitive response
(C)
inducible defence
(D)
detoxification
Official Scientific Justification: The plant sacrifices a small zone of tissue to isolate the pathogen.
Question 146
Unanswered
Gum deposition after wounding is seen in:
(A)
Acacia nilotica
(B)
maize
(C)
cactus
(D)
wheat
Official Scientific Justification: Leguminous trees such as Acacia release gum to trap microbes.
Question 147
Unanswered
The main component of the human immune system is the:
(A)
endocrine system
(B)
lymphatic system
(C)
digestive system
(D)
skeletal system
Official Scientific Justification: It contains lymph, lymph vessels and lymphoid organs.
Question 148
Unanswered
Primary lymphoid organs are:
(A)
spleen and tonsils
(B)
lymph nodes and appendix
(C)
bone marrow and thymus
(D)
Peyer's patches and spleen
Official Scientific Justification: Lymphocytes are produced and mature in the bone marrow and thymus.
Question 149
Unanswered
T lymphocytes complete their maturation in the:
(A)
bone marrow
(B)
spleen
(C)
thymus gland
(D)
tonsils
Official Scientific Justification: The hormone thymosin drives their maturation in the thymus.
Question 150
Unanswered
The thymus gland is located:
(A)
in the neck beside the thyroid
(B)
behind the sternum, in front of the trachea above the heart
(C)
in the upper left abdomen
(D)
in the lining of the small intestine
Official Scientific Justification: That is the thymus position; the upper left abdomen is the spleen.
Question 151
Unanswered
Which organ breaks down worn-out red blood cells using macrophages?
(A)
Tonsils
(B)
Thymus
(C)
Spleen
(D)
Lymph node
Official Scientific Justification: The spleen contains many macrophages that remove old cells and foreign particles.
Question 152
Unanswered
Peyer's patches are found in:
(A)
the stomach wall
(B)
the lower small intestine
(C)
the neck
(D)
the pharynx
Official Scientific Justification: They are aggregations of lymphoid cells in the intestinal mucosa.
Question 153
Unanswered
Lymph nodes:
(A)
filter lymph and store lymphocytes
(B)
secrete thymosin
(C)
produce red blood cells in adults
(D)
digest food
Official Scientific Justification: Nodes along lymph vessels clean lymph and hold lymphocytes and macrophages.
Question 154
Unanswered
Which of the following is an agranulocyte?
(A)
Neutrophil
(B)
Eosinophil
(C)
Basophil
(D)
Lymphocyte
Official Scientific Justification: Lymphocytes and monocytes lack visible granules.
Question 155
Unanswered
Cells that secrete antibodies are:
(A)
plasma cells
(B)
cytotoxic T cells
(C)
NK cells
(D)
macrophages
Official Scientific Justification: Plasma cells are differentiated B cells.
Question 156
Unanswered
The T cells that stimulate B cells to make antibodies are:
(A)
suppressor T cells
(B)
helper T cells
(C)
cytotoxic T cells
(D)
memory B cells
Official Scientific Justification: Helper T cells release interleukins that activate B cells.
Question 157
Unanswered
Perforin is a protein that:
(A)
neutralises toxins
(B)
forms pores in target cell membranes
(C)
carries amino acids
(D)
stimulates histamine release
Official Scientific Justification: Cytotoxic T cells and NK cells use perforin to punch holes in target cells.
Question 158
Unanswered
Natural killer cells mature in the:
(A)
thymus
(B)
bone marrow
(C)
spleen
(D)
lymph nodes
Official Scientific Justification: B and NK cells mature in the bone marrow.
Question 159
Unanswered
Monocytes change into:
(A)
plasma cells
(B)
mast cells
(C)
macrophages
(D)
T cells
Official Scientific Justification: Monocytes become macrophages when needed.
Question 160
Unanswered
Antigens are usually:
(A)
lipids of the host
(B)
proteins or glycoproteins on the pathogen surface
(C)
hormones
(D)
antibiotics
Official Scientific Justification: They identify the invader as foreign.
Question 161
Unanswered
Interferons are secreted by:
(A)
healthy bacteria
(B)
virus-infected cells
(C)
plasma cells
(D)
red blood cells
Official Scientific Justification: They warn and protect neighbouring cells by blocking viral replication.
Question 162
Unanswered
Proteins that attract phagocytes to the site of infection are:
(A)
interleukins
(B)
chemokines
(C)
interferons
(D)
complements
Official Scientific Justification: Chemokines recruit circulating phagocytes.
Question 163
Unanswered
Which class of immunoglobulin is NOT one of the five?
(A)
IgG
(B)
IgM
(C)
IgK
(D)
IgE
Official Scientific Justification: The classes are IgG, IgM, IgD, IgE, IgA.
Question 164
Unanswered
An antibody molecule is made of:
(A)
one polypeptide chain
(B)
two light chains only
(C)
two heavy and two light chains
(D)
four identical heavy chains
Official Scientific Justification: Two long and two short chains are joined by disulphide bonds.
Question 165
Unanswered
The specificity of an antibody depends on:
(A)
the constant region
(B)
the hinge only
(C)
the amino acids of the variable regions
(D)
the number of heavy chains
Official Scientific Justification: The binding-site shape is determined by the variable regions.
Question 166
Unanswered
The number of antigen-binding sites on one antibody (IgG) is:
(A)
1
(B)
2
(C)
3
(D)
4
Official Scientific Justification: One at each tip of the Y.
Question 167
Unanswered
Clumping of microbes by IgM is called:
(A)
precipitation
(B)
neutralisation
(C)
agglutination
(D)
lysis
Official Scientific Justification: IgM's many binding sites link several microbes together.
Question 168
Unanswered
Antibodies protect against viruses mainly by:
(A)
neutralisation
(B)
agglutination only
(C)
perforin release
(D)
histamine release
Official Scientific Justification: Binding to the viral coat prevents attachment and entry.
Question 169
Unanswered
Which of these belongs to the first line of defence?
(A)
Inflammation
(B)
Gastric hydrochloric acid
(C)
Plasma cells
(D)
Memory cells
Official Scientific Justification: Acid is a chemical barrier that kills swallowed microbes.
Question 170
Unanswered
Histamine is released by:
(A)
mast cells and basophils
(B)
B cells
(C)
neutrophils only
(D)
red blood cells
Official Scientific Justification: It starts the inflammatory response.
Question 171
Unanswered
Histamine causes blood vessels to:
(A)
constrict and become less permeable
(B)
dilate and become more permeable
(C)
clot
(D)
disintegrate
Official Scientific Justification: That produces redness, swelling and allows white cells to leave capillaries.
Question 172
Unanswered
Cilia in the respiratory tract:
(A)
make mucus
(B)
sweep mucus with trapped microbes out
(C)
kill microbes with enzymes
(D)
produce antibodies
Official Scientific Justification: Cilia beat and move mucus outward.
Question 173
Unanswered
Helper T cells recognise antigen when it is presented:
(A)
free in plasma
(B)
on MHC proteins on macrophages
(C)
on red blood cells
(D)
bound to antibodies
Official Scientific Justification: They only recognise processed antigen displayed with MHC.
Question 174
Unanswered
Antibodies are not effective against viruses inside cells because they:
(A)
are destroyed in the lymph
(B)
are too large to enter the cells
(C)
bind only to bacteria
(D)
are produced too slowly
Official Scientific Justification: Such infected cells must be killed by T cells.
Question 175
Unanswered
After the pathogen has been destroyed, the immune response is limited by:
(A)
helper T cells
(B)
cytotoxic T cells
(C)
suppressor T cells
(D)
macrophages
Official Scientific Justification: They secrete lymphokines that inhibit the response.
Question 176
Unanswered
The secondary immune response is faster because of:
(A)
more macrophages
(B)
memory cells
(C)
more interferon
(D)
thicker skin
Official Scientific Justification: Memory B and T cells made in the primary response are numerous and respond at once.
Question 177
Unanswered
Which statement about memory cells is correct?
(A)
They live a few days
(B)
They are made only by NK cells
(C)
They may survive for tens of years
(D)
They are made only after the second infection
Official Scientific Justification: They are formed in the primary response and live for decades.
Question 178
Unanswered
Chromosomes are made of:
(A)
DNA and lipids
(B)
DNA and proteins
(C)
RNA and carbohydrates
(D)
proteins only
Official Scientific Justification: Chromatin contains roughly equal amounts of DNA and protein.
Question 179
Unanswered
Scientists first expected proteins to be the genetic material because proteins:
(A)
are more stable than DNA
(B)
are built from 20 amino acids and are more varied
(C)
are found only in the nucleus
(D)
contain phosphorus
Official Scientific Justification: DNA has only four nucleotide types, so proteins looked more informative.
Question 180
Unanswered
Griffith worked with:
(A)
E. coli and phages
(B)
Pneumococcus and mice
(C)
yeast and fruit flies
(D)
tobacco mosaic virus
Official Scientific Justification: He injected S and R strains of pneumonia bacteria into mice.
Question 181
Unanswered
Mice injected with heat-killed S bacteria mixed with live R bacteria:
(A)
all survived
(B)
some died and live S bacteria were recovered
(C)
died with only R bacteria found
(D)
developed immunity
Official Scientific Justification: R bacteria were transformed to virulent S.
Question 182
Unanswered
The enzyme used by Avery's group to show DNA was the transforming material was:
(A)
protease
(B)
RNase
(C)
deoxyribonuclease
(D)
lipase
Official Scientific Justification: Destroying DNA stopped transformation; protease or RNase did not.
Question 183
Unanswered
In the Hershey–Chase experiment the phage protein was labelled with:
(A)
³²P
(B)
³⁵S
(C)
¹⁴C
(D)
³H
Official Scientific Justification: Protein contains sulphur and DNA contains phosphorus.
Question 184
Unanswered
Hershey and Chase found radioactivity from ³²P:
(A)
outside the bacteria
(B)
inside the bacteria
(C)
in neither
(D)
only in the phage coat
Official Scientific Justification: Viral DNA entered the bacteria.
Question 185
Unanswered
The genetic material of the AIDS virus is:
(A)
DNA
(B)
RNA
(C)
protein
(D)
lipid
Official Scientific Justification: Some viruses are exceptions with RNA genomes.
Question 186
Unanswered
Compared with a somatic cell, a gamete contains DNA amounting to:
(A)
double
(B)
the same
(C)
half
(D)
one quarter
Official Scientific Justification: Fusion of two gametes restores the somatic amount.
Question 187
Unanswered
The sugar of DNA is:
(A)
ribose
(B)
glucose
(C)
deoxyribose
(D)
fructose
Official Scientific Justification: It has one oxygen less than ribose.
Question 188
Unanswered
Which pair contains only purines?
(A)
A and T
(B)
A and G
(C)
C and T
(D)
G and C
Official Scientific Justification: Adenine and guanine have double rings.
Question 189
Unanswered
The phosphate group of a nucleotide is bonded to carbon number … of the sugar:
(A)
1′
(B)
2′
(C)
3′
(D)
5′
Official Scientific Justification: The base is on 1′; the next nucleotide links to 3′.
Question 190
Unanswered
Number of hydrogen bonds between guanine and cytosine:
(A)
1
(B)
2
(C)
3
(D)
4
Official Scientific Justification: A–T has two, G–C three.
Question 191
Unanswered
If a DNA molecule has 20% thymine, its guanine content is:
(A)
20%
(B)
30%
(C)
40%
(D)
60%
Official Scientific Justification: A = T = 20%, so G + C = 60%, G = 30%.
Question 192
Unanswered
Franklin used … to study DNA:
(A)
electron microscopy
(B)
X-ray diffraction
(C)
chromatography
(D)
centrifugation
Official Scientific Justification: Her photographs showed a helix with the backbone outside.
Question 193
Unanswered
Which statement about the DNA double helix is correct?
(A)
Strands are parallel
(B)
Bases face outward
(C)
Strands are antiparallel
(D)
A pairs with C
Official Scientific Justification: One runs 5′→3′ and the other 3′→5′.
Question 194
Unanswered
The number of base pairs per helical turn is about:
(A)
3
(B)
5
(C)
10
(D)
20
Official Scientific Justification: Ten nucleotide pairs per turn.
Question 195
Unanswered
All rungs of the DNA ladder have equal width because each pairs:
(A)
two purines
(B)
two pyrimidines
(C)
a purine with a pyrimidine
(D)
a base with a sugar
Official Scientific Justification: One double ring + one single ring each time.
Question 196
Unanswered
The enzyme that separates the DNA strands is:
(A)
ligase
(B)
helicase
(C)
primase
(D)
polymerase
Official Scientific Justification: It breaks hydrogen bonds between bases.
Question 197
Unanswered
DNA polymerase adds nucleotides to the … end of the new strand:
(A)
5′
(B)
3′
(C)
both ends
(D)
the middle
Official Scientific Justification: Synthesis proceeds 5′→3′.
Question 198
Unanswered
Primase synthesises short pieces of:
(A)
DNA
(B)
protein
(C)
RNA
(D)
lipid
Official Scientific Justification: RNA primers give polymerase a 3′ end to extend.
Question 199
Unanswered
Okazaki fragments are found on the:
(A)
leading strand
(B)
lagging strand
(C)
both equally
(D)
RNA only
Official Scientific Justification: The lagging strand is made discontinuously.
Question 200
Unanswered
Okazaki fragments are joined by:
(A)
helicase
(B)
primase
(C)
DNA ligase
(D)
RNA polymerase
Official Scientific Justification: Ligase seals the gaps.
Question 201
Unanswered
Each DNA molecule after replication contains:
(A)
two old strands
(B)
two new strands
(C)
one old and one new strand
(D)
mixed fragments of old and new
Official Scientific Justification: Replication is semi-conservative.
Question 202
Unanswered
Replication in eukaryotes starts at:
(A)
one point
(B)
the telomeres only
(C)
hundreds or thousands of points
(D)
the centromere only
Official Scientific Justification: This makes copying fast.
Question 203
Unanswered
In prokaryotes, replication begins:
(A)
at many sites
(B)
at the point of attachment of DNA to the plasma membrane
(C)
in the nucleolus
(D)
in the ribosomes
Official Scientific Justification: The circular DNA is attached at one point.
Question 204
Unanswered
About how many purine bases are lost daily from each human cell's DNA?
(A)
50
(B)
500
(C)
5,000
(D)
5 million
Official Scientific Justification: Heat breaks their bond to deoxyribose.
Question 205
Unanswered
DNA repair needs:
(A)
both strands damaged
(B)
one intact strand as template
(C)
RNA primers only
(D)
histones
Official Scientific Justification: The undamaged strand supplies the information.
Question 206
Unanswered
Why do RNA viruses mutate rapidly?
(A)
They have no genes
(B)
Single-stranded RNA cannot be repaired
(C)
They have histones
(D)
They replicate once
Official Scientific Justification: No second copy exists.
Question 207
Unanswered
Plasmids are:
(A)
small circular DNA molecules in bacteria
(B)
linear chromosomes
(C)
ribosomal subunits
(D)
proteins in chromatin
Official Scientific Justification: They are used as vectors in genetic engineering.
Question 208
Unanswered
Histones are rich in:
(A)
glutamate and aspartate
(B)
arginine and lysine
(C)
cysteine
(D)
glycine
Official Scientific Justification: Basic residues bind to the negative phosphates of DNA.
Question 209
Unanswered
The first level of DNA packing is the:
(A)
chromatid
(B)
nucleosome
(C)
loop
(D)
centromere
Official Scientific Justification: DNA wound around histone clusters.
Question 210
Unanswered
Which has DNA similar to that of prokaryotes?
(A)
Nucleus
(B)
Golgi apparatus
(C)
Mitochondria
(D)
Lysosomes
Official Scientific Justification: Mitochondrial and chloroplast DNA is circular and without histones.
Question 211
Unanswered
E. coli DNA, if straightened, is about … long:
(A)
1.4 mm
(B)
2 μm
(C)
2 m
(D)
14 cm
Official Scientific Justification: The cell is only about 2 μm long.
Question 212
Unanswered
The total DNA of a cell of an individual is its:
(A)
karyotype
(B)
genome
(C)
plasmid
(D)
chromatin
Official Scientific Justification: Genome = gene content.
Question 213
Unanswered
Promoters are found:
(A)
at the end of genes
(B)
at the beginning of genes
(C)
in ribosomes
(D)
in the cell wall
Official Scientific Justification: They mark where RNA synthesis begins.
Question 214
Unanswered
The salamander genome is about … times the human genome:
(A)
3
(B)
10
(C)
30
(D)
300
Official Scientific Justification: Most of the extra DNA is non-coding.
Question 215
Unanswered
Klinefelter syndrome has the chromosome formula:
(A)
44 + XO
(B)
44 + XXY
(C)
45 + XY
(D)
44 + XYY
Official Scientific Justification: One extra sex chromosome.
Question 216
Unanswered
Which agent is used to induce polyploidy?
(A)
Penicillin
(B)
Colchicine
(C)
Insulin
(D)
Ethanol
Official Scientific Justification: Mustard gas, nitrous acid and colchicine are inducing agents.
Question 217
Unanswered
Polyploidy is more common in:
(A)
mammals
(B)
plants
(C)
birds
(D)
humans
Official Scientific Justification: In animals it upsets sex determination.
Question 218
Unanswered
Collagen and keratin are examples of:
(A)
enzymes
(B)
structural proteins
(C)
hormones
(D)
antibodies
Official Scientific Justification: They form connective tissue, skin, hair and horns.
Question 219
Unanswered
Which of these is a regulatory protein?
(A)
Actin
(B)
Myosin
(C)
Insulin
(D)
Keratin
Official Scientific Justification: Hormones, enzymes and antibodies regulate processes.
Question 220
Unanswered
The amino acid with a second hydrogen atom as its R group is:
(A)
alanine
(B)
glycine
(C)
serine
(D)
lysine
Official Scientific Justification: Glycine is the simplest.
Question 221
Unanswered
Amino acids are joined by:
(A)
glycosidic bonds
(B)
ester bonds
(C)
peptide bonds
(D)
phosphodiester bonds
Official Scientific Justification: By dehydration reactions.
Question 222
Unanswered
The sugar of RNA is:
(A)
deoxyribose
(B)
ribose
(C)
glucose
(D)
fructose
Official Scientific Justification: Deoxyribose has one oxygen less.
Question 223
Unanswered
RNA contains … instead of thymine:
(A)
adenine
(B)
cytosine
(C)
uracil
(D)
guanine
Official Scientific Justification: Uracil pairs with adenine.
Question 224
Unanswered
A nucleic acid with A 12%, U 18%, G 39%, C 31% is:
(A)
double-stranded DNA
(B)
single-stranded DNA
(C)
RNA
(D)
can't be known
Official Scientific Justification: It contains uracil and has unequal A/U and G/C.
Question 225
Unanswered
Transcription begins when RNA polymerase binds to the:
(A)
ribosome
(B)
promoter
(C)
stop codon
(D)
anticodon
Official Scientific Justification: The promoter lies at the start of a gene.
Question 226
Unanswered
RNA polymerase assembles RNA in the direction:
(A)
3′→5′
(B)
5′→3′
(C)
both
(D)
random
Official Scientific Justification: It reads the template 3′→5′.
Question 227
Unanswered
In eukaryotes the number of RNA polymerases is:
(A)
one
(B)
two
(C)
three
(D)
four
Official Scientific Justification: Prokaryotes have one.
Question 228
Unanswered
The poly‑A tail of mRNA:
(A)
is translated to lysine
(B)
protects the mRNA from enzymes
(C)
binds the ribosome
(D)
is the start codon
Official Scientific Justification: It is not translated.
Question 229
Unanswered
Ribosomes are produced in the:
(A)
Golgi
(B)
nucleolus
(C)
lysosome
(D)
mitochondrion
Official Scientific Justification: rRNA genes are transcribed there.
Question 230
Unanswered
The number of different rRNA kinds in a ribosome is:
(A)
1
(B)
2
(C)
4
(D)
20
Official Scientific Justification: Four kinds are joined with about 70 polypeptides.
Question 231
Unanswered
The amino acid attaches to the tRNA at the sequence:
(A)
AUG
(B)
CCA at the 3′ end
(C)
anticodon
(D)
UAA
Official Scientific Justification: The acceptor end.
Question 232
Unanswered
The anticodon is found on:
(A)
mRNA
(B)
rRNA
(C)
tRNA
(D)
DNA
Official Scientific Justification: It pairs with the mRNA codon.
Question 233
Unanswered
In prokaryotes transcription and translation occur at the same time because:
(A)
they have ribosomes
(B)
there is no nuclear envelope
(C)
mRNA is short
(D)
there is no RNA polymerase
Official Scientific Justification: Ribosomes can attach to mRNA while it is still being made.
Question 234
Unanswered
The number of possible codons is:
(A)
16
(B)
20
(C)
61
(D)
64
Official Scientific Justification: 4³ = 64.
Question 235
Unanswered
The code is degenerate means:
(A)
it changes with time
(B)
several codons may code for one amino acid
(C)
a codon can code several amino acids
(D)
it differs among species
Official Scientific Justification: 64 codons for 20 amino acids.
Question 236
Unanswered
Which is the start codon?
(A)
UAA
(B)
AUG
(C)
UGA
(D)
GUA
Official Scientific Justification: It codes for methionine.
Question 237
Unanswered
Which is NOT a stop codon?
(A)
UAA
(B)
UAG
(C)
UGA
(D)
UGG
Official Scientific Justification: UGG codes for tryptophan.
Question 238
Unanswered
The universality of the genetic code supports:
(A)
separate origins of species
(B)
common ancestry of living organisms
(C)
spontaneous generation
(D)
acquired characters
Official Scientific Justification: The same codons code for the same amino acids everywhere.
Question 239
Unanswered
A polypeptide of 21 amino acids needs at least … nucleotides in its mRNA:
(A)
21
(B)
42
(C)
63
(D)
69
Official Scientific Justification: 21 × 3 = 63.
Question 240
Unanswered
A gene of 150 nucleotide pairs codes for at most … amino acids:
(A)
25
(B)
50
(C)
75
(D)
150
Official Scientific Justification: 150/3.
Question 241
Unanswered
The DNA triplet 3′‑TAC‑5′ is transcribed into the mRNA codon:
(A)
UAC
(B)
AUG
(C)
ATG
(D)
TAC
Official Scientific Justification: Complementary bases T→A, A→U, C→G.
Question 242
Unanswered
If a code were two-letter words, the number of codes would be:
(A)
4
(B)
8
(C)
16
(D)
64
Official Scientific Justification: 4² = 16, fewer than 20.
Question 243
Unanswered
Translation begins when mRNA binds to the:
(A)
large ribosomal subunit
(B)
small ribosomal subunit
(C)
DNA polymerase
(D)
tRNA of lysine
Official Scientific Justification: Then Met‑tRNA pairs with AUG and the large subunit joins.
Question 244
Unanswered
The first amino acid in a newly made polypeptide is usually:
(A)
lysine
(B)
glycine
(C)
methionine
(D)
alanine
Official Scientific Justification: Coded by AUG.
Question 245
Unanswered
The peptide bond between amino acids is formed by:
(A)
releasing factor
(B)
peptidyl transferase
(C)
helicase
(D)
ligase
Official Scientific Justification: It is part of the large ribosomal subunit.
Question 246
Unanswered
The site where the second tRNA first enters the ribosome is the:
(A)
P site
(B)
A site
(C)
E site
(D)
promoter
Official Scientific Justification: The aminoacyl site.
Question 247
Unanswered
Translation stops when the ribosome meets a:
(A)
start codon
(B)
stop codon
(C)
promoter
(D)
poly‑A tail only
Official Scientific Justification: A releasing factor binds.
Question 248
Unanswered
A cluster of ribosomes on one mRNA is a:
(A)
nucleosome
(B)
polyribosome
(C)
plasmid
(D)
chromatin
Official Scientific Justification: Also called polysome.
Question 249
Unanswered
Heating DNA to 100 °C causes:
(A)
breaking of peptide bonds
(B)
separation of strands by breaking hydrogen bonds
(C)
loss of bases
(D)
formation of RNA
Official Scientific Justification: Denaturation.
Question 250
Unanswered
Hybridisation can be used to:
(A)
estimate evolutionary relationships
(B)
make proteins
(C)
cut DNA
(D)
copy mRNA
Official Scientific Justification: More hybridisation means closer relationship.
Question 251
Unanswered
Restriction endonucleases are naturally produced by:
(A)
viruses
(B)
bacteria
(C)
plants
(D)
fungi only
Official Scientific Justification: They defend against viral DNA.
Question 252
Unanswered
Bacterial DNA is protected from its own restriction enzymes by:
(A)
histones
(B)
methylation
(C)
the nuclear membrane
(D)
RNA
Official Scientific Justification: Modification enzymes add methyl groups.
Question 253
Unanswered
Sticky ends are joined by:
(A)
helicase
(B)
DNA ligase
(C)
primase
(D)
reverse transcriptase
Official Scientific Justification: It seals the sugar–phosphate backbone.
Question 254
Unanswered
The enzyme that makes DNA from an RNA template is:
(A)
DNA polymerase
(B)
RNA polymerase
(C)
reverse transcriptase
(D)
restriction enzyme
Official Scientific Justification: It gives cDNA.
Question 255
Unanswered
Taq polymerase is used in PCR because it:
(A)
works at high temperature
(B)
cuts DNA
(C)
makes RNA
(D)
is found in humans
Official Scientific Justification: It survives repeated heating.
Question 256
Unanswered
The first recombinant DNA protein licensed for medical use was:
(A)
interferon
(B)
human insulin
(C)
growth hormone
(D)
haemoglobin
Official Scientific Justification: 1982, USA.
Question 257
Unanswered
The Human Genome Project was carried out in the period:
(A)
1950–1960
(B)
1975–1985
(C)
1990–2003
(D)
2010–2020
Official Scientific Justification: About 25,000 genes were identified.
Question 258
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Physiological vs. Structural Support in Plants?
(A)
Physiological support is temporary and completely dependent on water uptake into vacuoles via osmosis, while structural support is permanent via deposition of cellulose, lignin, or suberin
(B)
Physiological support involves permanent deposition of lignin in stone cells
(C)
Both physiological and structural supports disappear immediately when the plant wilts
(D)
Structural support relies solely on turgor pressure of living parenchyma
Official Scientific Justification: Physiological support is a reversible osmotic phenomenon affecting the entire cell, whereas structural support involves irreversible chemical thickening of cell walls.
Question 259
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Sliding Filament Theory of Muscle Contraction (Huxley)?
(A)
During sarcomere contraction, actin filaments slide over myosin filaments; the I-band and H-zone shorten, while the A-band length remains strictly constant
(B)
Both A-band and myosin filaments shrink by 50% in length
(C)
Z-lines move away from each other as the muscle contracts
(D)
Cross-bridges pull actin filaments outward away from the M-line
Official Scientific Justification: The A-band represents the constant total length of thick myosin filaments. Cross-bridges powered by ATP and Ca2+ pull thin actin filaments inward, causing the I-band and H-zone to narrow and Z-lines to approach each other.
Question 260
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Hormonal Regulation of Blood Glucose (Insulin and Glucagon)?
(A)
Beta cells of the islets of Langerhans secrete insulin to lower blood glucose by stimulating cellular uptake and glycogen synthesis, while alpha cells secrete glucagon to raise blood glucose by glycogenolysis
(B)
Alpha cells secrete insulin to elevate blood glucose levels
(C)
Insulin stimulates the breakdown of liver glycogen into glucose
(D)
Glucagon is secreted by the adrenal cortex under stress
Official Scientific Justification: Insulin and glucagon act antagonistically to maintain blood glucose homeostasis within the normal physiological range (80-120 mg/dL).
Question 261
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Parthenogenesis in Honeybees (Apis mellifera)?
(A)
The queen honeybee produces haploid drones (males, n) from unfertilized eggs via parthenogenesis, whereas diploid worker and queen females (2n) arise from fertilized eggs
(B)
Male drones arise from fertilized diploid zygotes (2n)
(C)
Female worker bees develop parthenogenetically without fertilization
(D)
Drones produce sperm cells by meiotic division
Official Scientific Justification: Parthenogenesis in honeybees generates haploid males (n) from unfertilized eggs. Drones produce sperm by mitosis so that their gametes are also haploid (n).
Question 262
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Plant Immunity: Role of Tyloses and Pre-existing Barriers?
(A)
Tyloses are balloon-like protrusions of xylem parenchyma cells that grow into xylem vessels through pits to block pathogen spread following vascular damage
(B)
Tyloses are biochemical antibodies synthesized by plant ribosomes
(C)
Tyloses accelerate the flow of infected sap to the leaves
(D)
Tyloses dissolve the fungal cell wall via chitinase enzymes
Official Scientific Justification: Tyloses represent an induced structural defense mechanism that mechanically obstructs the upward migration of pathogens through xylem vessels.
Question 263
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Chargaff's Rules of DNA Base Pairing?
(A)
In any double-stranded DNA molecule, the percentage of Adenine equals Thymine (%A = %T) and Guanine equals Cytosine (%G = %C), with total purines equaling pyrimidines (%A + %G = %T + %C = 50%)
(B)
Adenine bonds with Guanine via three hydrogen bonds
(C)
The percentage of %A + %T always equals 50% in all organisms
(D)
Uracil replaces Thymine in the double helix of nuclear DNA
Official Scientific Justification: Chargaff established that complementary base pairing in double-stranded DNA requires A to pair with T (2 hydrogen bonds) and G to pair with C (3 hydrogen bonds).
Question 264
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Transcription and Translation during Protein Synthesis?
(A)
RNA polymerase synthesizes mRNA from the antisense DNA template strand in the 5' to 3' direction, and translation occurs on ribosomes where tRNA anticodons bind mRNA codons
(B)
DNA polymerase transcribes mRNA in the cytoplasm
(C)
Translation begins at the UAA stop codon
(D)
tRNA molecules contain codons identical to DNA triplets
Official Scientific Justification: Transcription produces mRNA from the 3' to 5' DNA template. Translation on the ribosome translates codons into a specific amino acid sequence starting with AUG (Methionine).
Question 265
Unanswered
According to the Egyptian STEM biology syllabus, what is the exact scientific deduction regarding: Geological Dating and Index Fossils?
(A)
Index fossils must exhibit a wide geographic distribution and a short, well-defined chronological stratigraphic range to accurately correlate sedimentary rock layers
(B)
Index fossils must be restricted to a single local rock formation
(C)
Index fossils lived continuously throughout all geological eras
(D)
Index fossils are formed exclusively in intrusive igneous granite
Official Scientific Justification: An ideal index fossil allows geologists to identify and correlate the relative age of sedimentary strata across different continents.
Question 266
Unanswered
STEM Biology Problem 1: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 267
Unanswered
STEM Genetics Question 1: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 268
Unanswered
STEM Physiology Question 1: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 269
Unanswered
STEM Immunology Question 1: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 270
Unanswered
STEM Endocrinology Question 1: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 271
Unanswered
STEM Ecology Question 1: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 272
Unanswered
STEM Geology Question 1: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 273
Unanswered
STEM Molecular Genetics Question 1: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 274
Unanswered
STEM Biology Problem 2: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 275
Unanswered
STEM Genetics Question 2: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 276
Unanswered
STEM Physiology Question 2: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 277
Unanswered
STEM Immunology Question 2: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 278
Unanswered
STEM Endocrinology Question 2: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 279
Unanswered
STEM Ecology Question 2: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 280
Unanswered
STEM Geology Question 2: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 281
Unanswered
STEM Molecular Genetics Question 2: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 282
Unanswered
STEM Biology Problem 3: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 283
Unanswered
STEM Genetics Question 3: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 284
Unanswered
STEM Physiology Question 3: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 285
Unanswered
STEM Immunology Question 3: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 286
Unanswered
STEM Endocrinology Question 3: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 287
Unanswered
STEM Ecology Question 3: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 288
Unanswered
STEM Geology Question 3: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 289
Unanswered
STEM Molecular Genetics Question 3: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 290
Unanswered
STEM Biology Problem 4: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 291
Unanswered
STEM Genetics Question 4: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 292
Unanswered
STEM Physiology Question 4: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 293
Unanswered
STEM Immunology Question 4: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 294
Unanswered
STEM Endocrinology Question 4: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 295
Unanswered
STEM Ecology Question 4: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 296
Unanswered
STEM Geology Question 4: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 297
Unanswered
STEM Molecular Genetics Question 4: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 298
Unanswered
STEM Biology Problem 5: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 299
Unanswered
STEM Genetics Question 5: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 300
Unanswered
STEM Physiology Question 5: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 301
Unanswered
STEM Immunology Question 5: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 302
Unanswered
STEM Endocrinology Question 5: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 303
Unanswered
STEM Ecology Question 5: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 304
Unanswered
STEM Geology Question 5: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 305
Unanswered
STEM Molecular Genetics Question 5: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 306
Unanswered
STEM Biology Problem 6: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 307
Unanswered
STEM Genetics Question 6: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 308
Unanswered
STEM Physiology Question 6: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 309
Unanswered
STEM Immunology Question 6: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 310
Unanswered
STEM Endocrinology Question 6: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 311
Unanswered
STEM Ecology Question 6: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 312
Unanswered
STEM Geology Question 6: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 313
Unanswered
STEM Molecular Genetics Question 6: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 314
Unanswered
STEM Biology Problem 7: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 315
Unanswered
STEM Genetics Question 7: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 316
Unanswered
STEM Physiology Question 7: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 317
Unanswered
STEM Immunology Question 7: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 318
Unanswered
STEM Endocrinology Question 7: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 319
Unanswered
STEM Ecology Question 7: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 320
Unanswered
STEM Geology Question 7: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 321
Unanswered
STEM Molecular Genetics Question 7: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 322
Unanswered
STEM Biology Problem 8: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 323
Unanswered
STEM Genetics Question 8: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 324
Unanswered
STEM Physiology Question 8: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 325
Unanswered
STEM Immunology Question 8: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 326
Unanswered
STEM Endocrinology Question 8: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 327
Unanswered
STEM Ecology Question 8: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 328
Unanswered
STEM Geology Question 8: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 329
Unanswered
STEM Molecular Genetics Question 8: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 330
Unanswered
STEM Biology Problem 9: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 331
Unanswered
STEM Genetics Question 9: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 332
Unanswered
STEM Physiology Question 9: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 333
Unanswered
STEM Immunology Question 9: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 334
Unanswered
STEM Endocrinology Question 9: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 335
Unanswered
STEM Ecology Question 9: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 336
Unanswered
STEM Geology Question 9: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 337
Unanswered
STEM Molecular Genetics Question 9: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 338
Unanswered
STEM Biology Problem 10: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 339
Unanswered
STEM Genetics Question 10: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 340
Unanswered
STEM Physiology Question 10: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 341
Unanswered
STEM Immunology Question 10: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 342
Unanswered
STEM Endocrinology Question 10: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 343
Unanswered
STEM Ecology Question 10: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 344
Unanswered
STEM Geology Question 10: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 345
Unanswered
STEM Molecular Genetics Question 10: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 346
Unanswered
STEM Biology Problem 11: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 347
Unanswered
STEM Genetics Question 11: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 348
Unanswered
STEM Physiology Question 11: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 349
Unanswered
STEM Immunology Question 11: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 350
Unanswered
STEM Endocrinology Question 11: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 351
Unanswered
STEM Ecology Question 11: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 352
Unanswered
STEM Geology Question 11: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 353
Unanswered
STEM Molecular Genetics Question 11: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 354
Unanswered
STEM Biology Problem 12: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 355
Unanswered
STEM Genetics Question 12: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 356
Unanswered
STEM Physiology Question 12: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 357
Unanswered
STEM Immunology Question 12: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 358
Unanswered
STEM Endocrinology Question 12: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 359
Unanswered
STEM Ecology Question 12: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 360
Unanswered
STEM Geology Question 12: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 361
Unanswered
STEM Molecular Genetics Question 12: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 362
Unanswered
STEM Biology Problem 13: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 363
Unanswered
STEM Genetics Question 13: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 364
Unanswered
STEM Physiology Question 13: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 365
Unanswered
STEM Immunology Question 13: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 366
Unanswered
STEM Endocrinology Question 13: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 367
Unanswered
STEM Ecology Question 13: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 368
Unanswered
STEM Geology Question 13: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 369
Unanswered
STEM Molecular Genetics Question 13: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 370
Unanswered
STEM Biology Problem 14: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 371
Unanswered
STEM Genetics Question 14: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 372
Unanswered
STEM Physiology Question 14: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 373
Unanswered
STEM Immunology Question 14: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 374
Unanswered
STEM Endocrinology Question 14: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 375
Unanswered
STEM Ecology Question 14: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 376
Unanswered
STEM Geology Question 14: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 377
Unanswered
STEM Molecular Genetics Question 14: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 378
Unanswered
STEM Biology Problem 15: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 379
Unanswered
STEM Genetics Question 15: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 380
Unanswered
STEM Physiology Question 15: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 381
Unanswered
STEM Immunology Question 15: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 382
Unanswered
STEM Endocrinology Question 15: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 383
Unanswered
STEM Ecology Question 15: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 384
Unanswered
STEM Geology Question 15: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 385
Unanswered
STEM Molecular Genetics Question 15: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 386
Unanswered
STEM Biology Problem 16: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 387
Unanswered
STEM Genetics Question 16: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 388
Unanswered
STEM Physiology Question 16: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 389
Unanswered
STEM Immunology Question 16: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 390
Unanswered
STEM Endocrinology Question 16: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 391
Unanswered
STEM Ecology Question 16: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 392
Unanswered
STEM Geology Question 16: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 393
Unanswered
STEM Molecular Genetics Question 16: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 394
Unanswered
STEM Biology Problem 17: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 395
Unanswered
STEM Genetics Question 17: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 396
Unanswered
STEM Physiology Question 17: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 397
Unanswered
STEM Immunology Question 17: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 398
Unanswered
STEM Endocrinology Question 17: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 399
Unanswered
STEM Ecology Question 17: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 400
Unanswered
STEM Geology Question 17: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 401
Unanswered
STEM Molecular Genetics Question 17: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 402
Unanswered
STEM Biology Problem 18: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 403
Unanswered
STEM Genetics Question 18: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 404
Unanswered
STEM Physiology Question 18: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 405
Unanswered
STEM Immunology Question 18: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 406
Unanswered
STEM Endocrinology Question 18: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 407
Unanswered
STEM Ecology Question 18: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 408
Unanswered
STEM Geology Question 18: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 409
Unanswered
STEM Molecular Genetics Question 18: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 410
Unanswered
STEM Biology Problem 19: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 411
Unanswered
STEM Genetics Question 19: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 412
Unanswered
STEM Physiology Question 19: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 413
Unanswered
STEM Immunology Question 19: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 414
Unanswered
STEM Endocrinology Question 19: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 415
Unanswered
STEM Ecology Question 19: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 416
Unanswered
STEM Geology Question 19: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 417
Unanswered
STEM Molecular Genetics Question 19: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 418
Unanswered
STEM Biology Problem 20: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 419
Unanswered
STEM Genetics Question 20: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 420
Unanswered
STEM Physiology Question 20: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 421
Unanswered
STEM Immunology Question 20: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 422
Unanswered
STEM Endocrinology Question 20: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 423
Unanswered
STEM Ecology Question 20: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 424
Unanswered
STEM Geology Question 20: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 425
Unanswered
STEM Molecular Genetics Question 20: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 426
Unanswered
STEM Biology Problem 21: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 427
Unanswered
STEM Genetics Question 21: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 428
Unanswered
STEM Physiology Question 21: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 429
Unanswered
STEM Immunology Question 21: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 430
Unanswered
STEM Endocrinology Question 21: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 431
Unanswered
STEM Ecology Question 21: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 432
Unanswered
STEM Geology Question 21: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 433
Unanswered
STEM Molecular Genetics Question 21: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 434
Unanswered
STEM Biology Problem 22: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 435
Unanswered
STEM Genetics Question 22: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 436
Unanswered
STEM Physiology Question 22: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 437
Unanswered
STEM Immunology Question 22: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 438
Unanswered
STEM Endocrinology Question 22: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 439
Unanswered
STEM Ecology Question 22: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 440
Unanswered
STEM Geology Question 22: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 441
Unanswered
STEM Molecular Genetics Question 22: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 442
Unanswered
STEM Biology Problem 23: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 443
Unanswered
STEM Genetics Question 23: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 444
Unanswered
STEM Physiology Question 23: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 445
Unanswered
STEM Immunology Question 23: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 446
Unanswered
STEM Endocrinology Question 23: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 447
Unanswered
STEM Ecology Question 23: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 448
Unanswered
STEM Geology Question 23: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 449
Unanswered
STEM Molecular Genetics Question 23: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 450
Unanswered
STEM Biology Problem 24: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 451
Unanswered
STEM Genetics Question 24: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 452
Unanswered
STEM Physiology Question 24: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 453
Unanswered
STEM Immunology Question 24: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 454
Unanswered
STEM Endocrinology Question 24: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 455
Unanswered
STEM Ecology Question 24: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 456
Unanswered
STEM Geology Question 24: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 457
Unanswered
STEM Molecular Genetics Question 24: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 458
Unanswered
STEM Biology Problem 25: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 459
Unanswered
STEM Genetics Question 25: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 460
Unanswered
STEM Physiology Question 25: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 461
Unanswered
STEM Immunology Question 25: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 462
Unanswered
STEM Endocrinology Question 25: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 463
Unanswered
STEM Ecology Question 25: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 464
Unanswered
STEM Geology Question 25: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 465
Unanswered
STEM Molecular Genetics Question 25: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 466
Unanswered
STEM Biology Problem 26: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 467
Unanswered
STEM Genetics Question 26: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 468
Unanswered
STEM Physiology Question 26: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 469
Unanswered
STEM Immunology Question 26: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 470
Unanswered
STEM Endocrinology Question 26: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 471
Unanswered
STEM Ecology Question 26: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 472
Unanswered
STEM Geology Question 26: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 473
Unanswered
STEM Molecular Genetics Question 26: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 474
Unanswered
STEM Biology Problem 27: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 475
Unanswered
STEM Genetics Question 27: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 476
Unanswered
STEM Physiology Question 27: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 477
Unanswered
STEM Immunology Question 27: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 478
Unanswered
STEM Endocrinology Question 27: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 479
Unanswered
STEM Ecology Question 27: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 480
Unanswered
STEM Geology Question 27: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 481
Unanswered
STEM Molecular Genetics Question 27: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 482
Unanswered
STEM Biology Problem 28: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 483
Unanswered
STEM Genetics Question 28: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 484
Unanswered
STEM Physiology Question 28: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 485
Unanswered
STEM Immunology Question 28: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 486
Unanswered
STEM Endocrinology Question 28: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 487
Unanswered
STEM Ecology Question 28: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 488
Unanswered
STEM Geology Question 28: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 489
Unanswered
STEM Molecular Genetics Question 28: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 490
Unanswered
STEM Biology Problem 29: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 491
Unanswered
STEM Genetics Question 29: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 492
Unanswered
STEM Physiology Question 29: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 493
Unanswered
STEM Immunology Question 29: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 494
Unanswered
STEM Endocrinology Question 29: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 495
Unanswered
STEM Ecology Question 29: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 496
Unanswered
STEM Geology Question 29: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 497
Unanswered
STEM Molecular Genetics Question 29: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 498
Unanswered
STEM Biology Problem 30: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 499
Unanswered
STEM Genetics Question 30: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 500
Unanswered
STEM Physiology Question 30: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 501
Unanswered
STEM Immunology Question 30: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 502
Unanswered
STEM Endocrinology Question 30: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 503
Unanswered
STEM Ecology Question 30: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 504
Unanswered
STEM Geology Question 30: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 505
Unanswered
STEM Molecular Genetics Question 30: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 506
Unanswered
STEM Biology Problem 31: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 507
Unanswered
STEM Genetics Question 31: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 508
Unanswered
STEM Physiology Question 31: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 509
Unanswered
STEM Immunology Question 31: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 510
Unanswered
STEM Endocrinology Question 31: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 511
Unanswered
STEM Ecology Question 31: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 512
Unanswered
STEM Geology Question 31: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 513
Unanswered
STEM Molecular Genetics Question 31: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 514
Unanswered
STEM Biology Problem 32: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 515
Unanswered
STEM Genetics Question 32: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 516
Unanswered
STEM Physiology Question 32: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 517
Unanswered
STEM Immunology Question 32: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 518
Unanswered
STEM Endocrinology Question 32: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 519
Unanswered
STEM Ecology Question 32: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 520
Unanswered
STEM Geology Question 32: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 521
Unanswered
STEM Molecular Genetics Question 32: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 522
Unanswered
STEM Biology Problem 33: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 523
Unanswered
STEM Genetics Question 33: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 524
Unanswered
STEM Physiology Question 33: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 525
Unanswered
STEM Immunology Question 33: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 526
Unanswered
STEM Endocrinology Question 33: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 527
Unanswered
STEM Ecology Question 33: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 528
Unanswered
STEM Geology Question 33: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 529
Unanswered
STEM Molecular Genetics Question 33: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 530
Unanswered
STEM Biology Problem 34: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 531
Unanswered
STEM Genetics Question 34: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 532
Unanswered
STEM Physiology Question 34: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 533
Unanswered
STEM Immunology Question 34: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 534
Unanswered
STEM Endocrinology Question 34: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 535
Unanswered
STEM Ecology Question 34: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 536
Unanswered
STEM Geology Question 34: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 537
Unanswered
STEM Molecular Genetics Question 34: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 538
Unanswered
STEM Biology Problem 35: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 539
Unanswered
STEM Genetics Question 35: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 540
Unanswered
STEM Physiology Question 35: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 541
Unanswered
STEM Immunology Question 35: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 542
Unanswered
STEM Endocrinology Question 35: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 543
Unanswered
STEM Ecology Question 35: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 544
Unanswered
STEM Geology Question 35: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 545
Unanswered
STEM Molecular Genetics Question 35: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 546
Unanswered
STEM Biology Problem 36: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 547
Unanswered
STEM Genetics Question 36: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 548
Unanswered
STEM Physiology Question 36: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 549
Unanswered
STEM Immunology Question 36: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 550
Unanswered
STEM Endocrinology Question 36: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 551
Unanswered
STEM Ecology Question 36: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 552
Unanswered
STEM Geology Question 36: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 553
Unanswered
STEM Molecular Genetics Question 36: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 554
Unanswered
STEM Biology Problem 37: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 555
Unanswered
STEM Genetics Question 37: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 556
Unanswered
STEM Physiology Question 37: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 557
Unanswered
STEM Immunology Question 37: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 558
Unanswered
STEM Endocrinology Question 37: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 559
Unanswered
STEM Ecology Question 37: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 560
Unanswered
STEM Geology Question 37: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 561
Unanswered
STEM Molecular Genetics Question 37: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 562
Unanswered
STEM Biology Problem 38: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 563
Unanswered
STEM Genetics Question 38: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 564
Unanswered
STEM Physiology Question 38: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 565
Unanswered
STEM Immunology Question 38: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 566
Unanswered
STEM Endocrinology Question 38: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 567
Unanswered
STEM Ecology Question 38: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 568
Unanswered
STEM Geology Question 38: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 569
Unanswered
STEM Molecular Genetics Question 38: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 570
Unanswered
STEM Biology Problem 39: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 571
Unanswered
STEM Genetics Question 39: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 572
Unanswered
STEM Physiology Question 39: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 573
Unanswered
STEM Immunology Question 39: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 574
Unanswered
STEM Endocrinology Question 39: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 575
Unanswered
STEM Ecology Question 39: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 576
Unanswered
STEM Geology Question 39: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 577
Unanswered
STEM Molecular Genetics Question 39: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 578
Unanswered
STEM Biology Problem 40: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 579
Unanswered
STEM Genetics Question 40: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 580
Unanswered
STEM Physiology Question 40: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 581
Unanswered
STEM Immunology Question 40: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 582
Unanswered
STEM Endocrinology Question 40: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 583
Unanswered
STEM Ecology Question 40: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 584
Unanswered
STEM Geology Question 40: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 585
Unanswered
STEM Molecular Genetics Question 40: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 586
Unanswered
STEM Biology Problem 41: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 587
Unanswered
STEM Genetics Question 41: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 588
Unanswered
STEM Physiology Question 41: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 589
Unanswered
STEM Immunology Question 41: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 590
Unanswered
STEM Endocrinology Question 41: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 591
Unanswered
STEM Ecology Question 41: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 592
Unanswered
STEM Geology Question 41: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 593
Unanswered
STEM Molecular Genetics Question 41: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 594
Unanswered
STEM Biology Problem 42: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 595
Unanswered
STEM Genetics Question 42: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 596
Unanswered
STEM Physiology Question 42: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 597
Unanswered
STEM Immunology Question 42: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 598
Unanswered
STEM Endocrinology Question 42: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 599
Unanswered
STEM Ecology Question 42: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 600
Unanswered
STEM Geology Question 42: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 601
Unanswered
STEM Molecular Genetics Question 42: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 602
Unanswered
STEM Biology Problem 43: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 603
Unanswered
STEM Genetics Question 43: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 604
Unanswered
STEM Physiology Question 43: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 605
Unanswered
STEM Immunology Question 43: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 606
Unanswered
STEM Endocrinology Question 43: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 607
Unanswered
STEM Ecology Question 43: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 608
Unanswered
STEM Geology Question 43: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 609
Unanswered
STEM Molecular Genetics Question 43: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.
Question 610
Unanswered
STEM Biology Problem 44: A double-stranded DNA segment contains 1,200 nucleotides, of which 240 are Adenine. What is the total number of Cytosine bases and hydrogen bonds in this segment?
(A)
360 Cytosine bases and 1,560 total hydrogen bonds
(B)
240 Cytosine bases and 1,200 hydrogen bonds
(C)
480 Cytosine bases and 1,800 hydrogen bonds
(D)
120 Cytosine bases and 960 hydrogen bonds
Official Scientific Justification: Total nucleotides = 1,200. A = 240, so T = 240. (A + T) = 480. Therefore, (G + C) = 1,200 - 480 = 720, so C = G = 360. Hydrogen bonds = (240 × 2) + (360 × 3) = 480 + 1,080 = 1,560.
Question 611
Unanswered
STEM Genetics Question 44: What is the minimum number of tRNA anticodons required to translate an mRNA transcript containing 150 codons, terminating with a UAG stop codon?
(A)
149 tRNA molecules (stop codons do not code for amino acids or tRNAs)
(B)
150 tRNA molecules
(C)
151 tRNA molecules
(D)
75 tRNA molecules
Official Scientific Justification: The transcript has 150 codons. The final codon (UAG) is a termination codon recognized by release factors, not tRNA. Thus, exactly 149 amino acids are translated by 149 tRNAs.
Question 612
Unanswered
STEM Physiology Question 44: In a skeletal muscle motor unit consisting of 1 motor neuron and 50 muscle fibers, what is the minimum number of ATP molecules required for one complete contraction-relaxation cycle per cross-bridge?
(A)
2 ATP molecules (one for cross-bridge detachment and one for Ca2+ active transport back into the sarcoplasmic reticulum)
(B)
0 ATP molecules (relaxation is completely passive)
(C)
10 ATP molecules per fiber
(D)
1 ATP molecule shared across all 50 fibers
Official Scientific Justification: ATP is required both to detach myosin cross-bridges from actin during relaxation and to power Ca2+-ATPase pumps restoring calcium into the sarcoplasmic reticulum.
Question 613
Unanswered
STEM Immunology Question 44: Which immune cells are directly responsible for secreting perforin proteins and granzymes to lyse virally infected cells and tumor cells?
(A)
Cytotoxic T-cells (CD8+ Tc) and Natural Killer (NK) cells
(B)
Helper T-cells (CD4+ Th) exclusively
(C)
Plasma B-cells secreting IgG
(D)
Mast cells releasing histamine
Official Scientific Justification: Active Cytotoxic T-lymphocytes (Tc) and NK cells synthesize perforin to create transmembrane pores in target cells, allowing granzymes to enter and trigger programmed cell death (apoptosis).
Question 614
Unanswered
STEM Endocrinology Question 44: A patient suffers from increased metabolic rate, weight loss, nervousness, and protruding eyes (exophthalmos). Which endocrine condition is most likely diagnosed?
(A)
Exophthalmic goiter (Hyperthyroidism caused by excessive thyroxine secretion)
(B)
Simple endemic goiter due to iodine deficiency
(C)
Myxedema resulting from severe hypothyroidism in adults
(D)
Cushing's syndrome from elevated cortisol
Official Scientific Justification: Hyperthyroidism (exophthalmic goiter) elevates cellular respiration and basal metabolic rate, causing heat intolerance, weight loss despite high appetite, nervousness, and ocular protrusion.
Question 615
Unanswered
STEM Ecology Question 44: In an arid desert ecosystem, what morphological adaptation enables xerophytic plants like Acacia and Opuntia to survive severe water scarcity?
(A)
Extensive deep or horizontal root systems, thick waxy cutin layers, and sunken stomata
(B)
Broad thin leaves with dense stomata on both surfaces
(C)
Absence of xylem vessels and thin cellulose walls
(D)
Rapid continuous transpiration during midday heat
Official Scientific Justification: Desert xerophytes minimize transpiration via thick cuticles, reduced spine-like leaves, and sunken stomata, while maximizing water absorption with deep taproots reaching the water table.
Question 616
Unanswered
STEM Geology Question 44: Which type of geological fault is formed when hanging-wall rocks slide downward relative to the footwall under tensional stress?
(A)
Normal fault resulting from crustal extensional (tensional) forces
(B)
Reverse fault caused by lateral compressional stress
(C)
Thrust fault with an inclination angle less than 45 degrees
(D)
Strike-slip fault with purely horizontal displacement
Official Scientific Justification: In a normal fault, tensional stress pulls the crust apart, causing the hanging wall to move downward relative to the footwall along the fault plane.
Question 617
Unanswered
STEM Molecular Genetics Question 44: Why are sticky ends produced by restriction endonucleases essential for constructing recombinant DNA plasmids?
(A)
They have single-stranded overhangs that readily form complementary hydrogen bonds with matching foreign DNA fragments
(B)
They permanently destroy DNA ligase activity
(C)
They prevent plasmids from entering bacterial cells
(D)
They mutate bacterial resistance genes permanently
Official Scientific Justification: Restriction enzymes cut palindromic sequences producing staggered 'sticky ends' with complementary overhanging nucleotides that base-pair with foreign DNA before ligation.