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Course: AQA A Level Biology 7402
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AQA A Level Biology 7402

1. Biological Molecules

0/102

2. Cell Structure

0/95

3. Exchange and Transport

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4. Genetics, Variation and Interdependence

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5. Energy Transfers In and Between Organisms (A Level only)

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6. Organisms Respond to Changes in their Environments (A Level only)

0/93

7. Genetics, Populations, Evolution and Ecosystems (A Level only)

0/55

8. The Control of Gene Expression (A Level only)

0/72

9. Exam Guidance and Skills

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Quiz

1.4.8 Limiting Factors Affecting Enzymes- pH – Unit exam questions

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  • Questions count: 18
  • Passing grade: B+
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1.

A competitive inhibitor

binds elsewhere
increases the rate
denatures the enzyme
binds to the active site and competes with the substrate
2.
IGCSE Biology 1.3 Dna in Classification - Question 3
IGCSE Biology 1.3 Dna in Classification - Question 3
A
B
C
D
3.
Why does enzyme activity fall sharply at high temperatures?
Substrate molecules move slower
Activation energy increases
The enzyme denatures as bonds holding its shape break
ATP runs out
4.

An enzyme–substrate complex is

the product of the reaction
an inhibitor
a coenzyme
the temporary structure formed when a substrate binds to the active site
5.
Most of the ATP creation during respiration occurs as a result of what driving force?
Most of the ATP creation during respiration occurs as a result of what driving force?
Electrons moving down a concentration gradient
Electrons moving down the electron transport chain
Protons moving down a concentration gradient
Sodium ions moving down a concentration gradient
Movement of pyruvate from the cytoplasm into the mitochondria
6.
The fluid mosaic model describes the membrane as
a phospholipid bilayer with proteins that can move laterally
a rigid protein sheet
a layer of cellulose
a single layer of lipids
7.
IGCSE Biology 4.2 Dna Molecule - Question 3
IGCSE Biology 4.2 Dna Molecule - Question 3
A
B
C
D
8.
If replication were conservative, what would generation 1 show?
One intermediate band
One heavy band and one light band
Only light DNA
Only heavy DNA
9.
The diagram shows two replication models. Which model is semiconservative?
Dr Dabour Hub Academy - figure 1
Model 1
Model 2
Both models
Neither model
10.
What happens to an enzyme above its optimum temperature?
It works faster forever
It becomes denatured
It changes substrate
It becomes a carbohydrate
11.
In the pipe-cleaner model, students forget to twist beads between colours. Which process is missing from their model?
Crossing over
DNA replication
Cytokinesis
Fertilisation
12.
Pepsin works best in the stomach because:
Its optimum pH is about 2
Its optimum temperature is 60 °C
It digests starch
Its optimum pH is about 9
13.
Pepsin works in the stomach at pH 2. If moved to the small intestine at pH 8, it would
work faster
stop working because its shape changes
change into trypsin
work at the same rate
14.
Which enzyme works best at pH 2?
Salivary amylase
Trypsin
Pepsin
Pancreatic lipase
15.
The graph shows three enzymes' activity against pH. Which enzyme would work best in an acidic stomach?
Dr Dabour Hub Academy - figure 2
Amylase
Trypsin
Pepsin
All equally
16.
Lysosomal enzyme activity at two pH values is shown. What is the safety benefit of this?
The enzymes work best in cytosol
Enzymes destroy the lysosome at pH 5
Leaked enzymes are much less active in neutral cytosol, so the cell is protected
pH has no effect
17.

Most enzymes in the human body work best at a pH near

7
1
14
3
18.
In a test of how pH affects enzyme activity, keeping temperature the same makes it a _____.
dependent variable
constant
hypothesis
control group
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Part of 1. Biological Molecules — see every lesson and quiz in this unit.
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