2.8Structures and Functions in Living Organisms
Transport — Edexcel Modular - OL Revision Notes & Topical Questions
5 min read 15 parts Lesson 8 of 12 2 quizzes
Lesson summary
Transport Edexcel O Level Modular Biology notes: understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cellLeft ventricle wall is thicker – pumps to whole body.Fetal haemoglobin has higher affinity for O₂ than adult haemog…
- Double circulation
- Tissue fluid
- Bohr shift
- Cardiac cycle
- Give / State / Name
- Evaluate / Assess
Part 1 of 12Key features at a glance
1
Left ventricle wall is thicker – pumps to whole body.
2
Fetal haemoglobin has higher affinity for O₂ than adult haemoglobin.
3
CO₂ transported mostly as HCO₃⁻ (carbonic anhydrase in red cells).
4
Chloride shift keeps red cells electrically neutral.
Part 2 of 12Detailed topic notes 1 of 7
1
understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell
2
understand the need for a transport system in multicellular organisms
3
describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant
4
describe the role of xylem in transporting water and mineral ions from the roots to other parts of the plant understand how the rate of transpiration is affected by changes in humidity, wind speed, temperature and light intensity practical: investigate the role of environmental factors in determining the rate of transpiration from a leafy shoot
Part 3 of 12Detailed topic notes 2 of 7
1
describe the composition of the blood
- red blood cells
- white blood cells
- platelets and plasma
2
understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy
3
understand how adaptations of red blood cells make them suitable for the transport of oxygen, including shape, the absence of a nucleus and the presence of haemoglobin
4
understand how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen understand how vaccination results in the manufacture of memory cells,
- which enable future antibody production to the pathogen to occur sooner, faster and in greater quantity
Part 4 of 12Detailed topic notes 3 of 7
1
describe the structure of the heart and how it functions
2
explain how the heart rate changes during exercise and under the influence of adrenaline
3
understand how factors may increase the risk of developing coronary heart disease
4
understand how the structure of arteries, veins and capillaries relate to their function
Part 5 of 12Detailed topic notes 4 of 7
1
understand the general structure of the circulation system, including the blood vessels to and from the heart and lungs, liver and kidneys (i)
2
understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf
3
know the excretory products of the lungs, kidneys and skin (organs of excretion) (j)
4
understand how organisms are able to respond to changes in their environment
Part 6 of 12Detailed topic notes 5 of 7
1
understand that homeostasis is the maintenance of a constant internal environment, and that body water content and body temperature are both examples of homeostasis
2
understand that a co-ordinated response requires a stimulus, a receptor and an effector
3
understand that plants respond to stimuli
4
describe the geotropic and phototropic responses of roots and stems
Part 7 of 12Detailed topic notes 6 of 7
1
understand the role of auxin in the phototropic response of stems (j)
2
describe how nervous and hormonal communication control responses and understand the differences between the two systems
3
understand that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves
4
understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses
Part 8 of 12Detailed topic notes 7 of 7
1
understand the role of neurotransmitters at synapses
2
describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object
3
describe the structure and function of the eye as a receptor
4
understand the function of the eye in focusing on near and distant objects, and in responding to changes in light intensity
Part 9 of 12Process & sequence
- SAN
- Atria contract
- AVN (delay)
- Bundle of His
- Purkyne fibres
- Ventricles contract from apex
1
Atrial systole: atria contract, AV valves open.
2
Ventricular systole: AV valves close (lub), blood forced into arteries.
3
Semilunar valves open.
4
Diastole: ventricles relax, semilunar valves close (dub).
5
Heart fills with blood.
Part 10 of 12Essential review
1
The pacemaker is the SAN.
2
High CO₂ causes the Bohr shift.
3
Capillary walls are one cell thick.
4
describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation
5
understand the sources, roles and effects of the following hormones adrenaline insulin testosterone progesterone and oestrogen
Part 11 of 12Questions to test yourself
Q1. Complete the statement: The pacemaker is the ______.
- SAN
- Vein
- Haemoglobin
- Cardiac cycle
Show answer
SAN
Q2. Which statement best describes Double circulation?
1
Plasma forced out of capillaries by hydrostatic pressure.
2
Blood passes through the heart twice per circuit.
3
Thick muscular elastic wall; carries blood away from the heart at high pressure.
4
Thin wall, valves, large lumen; blood to heart at low pressure.
Show answer
Blood passes through the heart twice per circuit.
Q3. Which key term matches this description: "Protein carrying oxygen as oxyhaemoglobin."
- Haemoglobin
- Bohr shift
- Cardiac cycle
- Artery
Show answer
Haemoglobin
Part 12 of 12Compare: Compare
| Vessel | Wall | Lumen | Pressure | Valves | Function |
|---|---|---|---|---|---|
| Artery | Thick; elastic + smooth muscle | Narrow | High, pulsatile | No (except semilunar at base) | Carry blood from heart |
| Arteriole | Muscular | Small | Falling | No | Control flow to capillaries |
| Capillary | Endothelium only | ~7 µm | Low | No | Exchange of substances |
| Venule | Thin | Small | Low | Some | Collect from capillaries |
| Vein | Thin, little muscle | Wide | Very low | Yes | Return blood to heart |
Key terms
Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Double circulation · Artery · Vein · Capillary · Tissue fluid · Haemoglobin · Bohr shift · Cardiac cycle
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. eukaryotic/prokaryotic, enzyme–substrate complex, active site, complementary).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
Marked practiceQuizzes for this lesson
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