AQA GCSE Biology Biology Paper 1 (Higher), June 2025: Question 5
16 marks · Standard Demand difficulty · Short Answer
Answer questions on the human circulatory system, magnification calculations of red blood cells, blood vessels and heart anatomy, and cellular respiration during exercise.
Practise this questionQuestion
Question text
05 This question is about the human circulatory system.
05.1 Blood plasma transports blood cells around the body.
Give one other function of blood plasma.
Do not refer to oxygen in your answer.
[1 mark]
05.2 Figure 5 shows a red blood cell.
Figure 5
The image of the red blood cell in Figure 5 is magnified 7200 times.
Calculate the real diameter of the red blood cell.
Give your answer in micrometres (μm).
[5 marks]
Real diameter = μm
Figure 6 shows the heart.
Figure 6
05.3 Blood pressure is a measure of the force of the blood against the walls of the blood
vessels.
Table 5 shows information about the different types of blood vessel shown
in Figure 6.
[2 marks]
Table 5
Pressure of blood travelling through
Blood vessel in Figure 6
blood vessel in arbitrary units
4 D
Complete Table 5 using the correct letters from Figure 6.
One row has been completed for you.
05.4 Name blood vessel D in Figure 6.
[1 mark]
05.5 Describe the structure of the walls of an artery.
[1 mark]
An athlete ran on a running machine.
The athlete:
• reached their maximum intensity of exercise and then stopped exercising
• had their use of oxygen recorded
• had the lactic acid concentration in their blood recorded.
05.6 During the exercise the athlete respired aerobically and anaerobically.
Explain why anaerobic respiration is less efficient than aerobic respiration.
[2 marks]
Figure 7 shows the athlete’s use of oxygen and the lactic acid concentration of blood
during exercise and after exercise.
Figure 7
05.7 Explain why the use of oxygen remained high after the athlete stopped exercising.
[2 marks]
05.8 Some athletes regularly exercise in conditions that increase the number of red
blood cells.
Explain why having an increased number of red blood cells is an advantage to
an athlete.
[2 marks]
Mark scheme
Show the mark scheme
Question 5
AO /
Question Answers Extra information Mark
Spec Ref.
05.1 (to) transport / carry hormones / allow (to) transport / carry other 1 AO1
antibodies / proteins / ions / correctly named substances 4.2.2.3
enzymes / urea / glucose / allow (to) transport / carry
carbon dioxide platelets
ignore nutrients / waste / oxygen
AO /
Spec Ref.
05.2 recall of equation allow
magnification = magnification = 1 AO1
size of image diameter of image
size of real object diameter of real object
ignore use of equation triangle
rearrangement of equation allow
size of real object = diameter of real object = 1 AO2
size of image diameter of image
magnification magnification
substitution
6.3 allow substitution of incorrectly 1 AO2
7200 converted value
0.000875 (cm) allow answer using incorrectly 1 AO2
converted value
conversion
8.75 (μm) allow 8.8 (μm) 1 AO2
allow conversion to μm at any
stage 4.1.1.5
ignore further rounding
AO /
Question Answers Mark
Spec Ref.
05.3 2 AO3
Pressure of blood travelling 4.2.2.2
through vessel in arbitrary Blood vessel in Figure X
units
5 A
18 B
120 C
allow 1 mark for 1 or 2 correct answers
ignore names of blood vessels
AO /
Spec Ref.
05.4 pulmonary vein 1 AO1
4.2.2.2
AO /
Spec Ref.
05.5 thick elastic / muscle (layer) ignore thick wall unqualified 1 AO1
do not accept reference to cell 4.2.2.2
walls
ignore has no valves
AO /
Spec Ref.
05.6 less energy released / allow more molecules of glucose 1 AO1
transferred (per molecule of need to be broken down to 4.4.2.1
glucose) release / transfer equivalent
energy
do not accept less energy
produced / made / created
do not accept no energy
released
do not accept less energy
released for respiration
(due to) incomplete breakdown / allow glucose only broken down 1
oxidation of glucose to lactic acid
AO /
Spec Ref.
05.7 (the athlete has an) oxygen debt allow the lactic acid 1 AO2
concentration is high 4.4.2.1
4.4.2.2
(so more) oxygen is required to allow (so more) oxygen is 1 21
oxidise lactic acid required to remove lactic acid
allow (so more) oxygen is
required to break down lactic
acid
ignore reference to oxygen
being used to convert lactic acid
back to glucose (in the liver)
ignore reference to liver as the
site of lactic acid oxidation
AO /
Spec Ref.
05.8 (there is) more haemoglobin so allow more oxyhaemoglobin (is 1 AO2
more oxygen (carried / bound) formed) 4.4.2.1
4.2.2.3
(athlete can do) more aerobic allow (athlete will do) less 1
respiration to transfer / release anaerobic respiration which
(more) energy transfers / releases less energy
or allow (athlete will do) less
(athlete can do) more aerobic anaerobic respiration which
respiration so less muscle would (otherwise) result in
fatigue / cramp muscle fatigue / cramp
do not accept (athlete can do)
more anaerobic respiration
do not accept energy produced
/ made / created
do not accept energy released
for respiration
Total Question 5 16
How to answer it
Human Circulatory System & Exercise Physiology
What this question tests:
- Blood components & functions: Specific solutes transported in blood plasma and adaptations of red blood cells.
- Microscopy calculations: Using the formula Magnification = Image size ÷ Actual size , including multistep rearrangements and metric unit conversions ( cm to µm ).
- Heart anatomy & hemodynamics: Identifying major vessels (vena cava, pulmonary artery, aorta, pulmonary vein) and deducing blood pressure differences across pulmonary and systemic circuits.
- Blood vessel adaptations: Key histological features of artery walls.
- Aerobic vs anaerobic respiration: Energy yield per glucose molecule, oxygen debt repayment, and exercise adaptations.
Question 05.1: Functions of Blood Plasma
1 Mark • Assessment Objective: AO1
✅ Mark Scheme Answers
Any one of the following transported substances:
- Carbon dioxide
- Glucose
- Urea
- Hormones
- Antibodies / proteins
- Ions / mineral salts
- Platelets
❌ Common Errors & Traps
- Oxygen: The question specifically instructed: "Do not refer to oxygen". Oxygen is carried by haemoglobin inside red blood cells, not dissolved in large quantities in plasma.
- Vague answers: Giving generic terms like "nutrients" or "waste" awards 0 marks. Name specific molecules (e.g. glucose, urea).
Question 05.2: Calculating Real Diameter of a Red Blood Cell
5 Marks • Assessment Objective: AO1 / AO2
📐 Step-by-Step Calculation
- State formula:
Magnification = Size of image ÷ Size of real object [1 mark] - Rearrange formula for real size:
Size of real object = Size of image ÷ Magnification [1 mark] - Substitute given values:
Image diameter = 6.3 cm , Magnification = 7200
Real diameter = 6.3 ÷ 7200 [1 mark] - Calculate diameter in original units (cm):
Real diameter = 0.000875 cm (or 8.75 × 10⁻⁴ cm ) [1 mark] - Convert to micrometres (µm):
1 cm = 10 mm = 10,000 µm (multiply by 10,000)
0.000875 × 10,000 = 8.75 µm (allow 8.8 µm ) [1 mark]
🧠 Exam Technique: Unit Conversions
You can also convert before dividing:
- Convert image size first: 6.3 cm × 10,000 = 63,000 µm
- Divide by magnification: 63,000 ÷ 7200 = 8.75 µm
- Always write the rearranged formula down before touching your calculator to secure method marks even if a calculation slips!
❌ Common Mistakes
- Using an incorrect conversion factor (e.g. dividing by 1000 instead of multiplying by 10,000).
- Inverting the equation (doing Magnification ÷ Image size).
Question 05.3: Matching Blood Vessels to Pressure
2 Marks • Assessment Objective: AO3
💡 Key Knowledge: Blood Pressure in the Great Vessels
- Vessel A (Vena Cava): Vein returning deoxygenated blood to the right atrium → Very low pressure (~5 units).
- Vessel B (Pulmonary Artery): Artery pumping blood to delicate lung capillaries → Medium/low arterial pressure (~18 units).
- Vessel C (Aorta): Main artery pumping blood to the entire systemic body under high force from thick left ventricle → Highest pressure (~120 units).
- Vessel D (Pulmonary Vein): Given in table as 4 units → Lowest pressure.
✅ Completed Table 5
| Pressure of blood (arbitrary units) | Blood vessel in Figure 6 |
|---|---|
| 4 | D (Given) |
| 5 | A (Vena Cava) |
| 18 | B (Pulmonary Artery) |
| 120 | C (Aorta) |
Question 05.4: Identifying Vessel D
1 Mark • Assessment Objective: AO1
✅ Mark Scheme Answer
Pulmonary vein
🧠 Visual Clues
Remember anatomical orientation is reversed (looking at a patient facing you):
- Left side of image = Right side of heart (Vessels A and B).
- Right side of image = Left side of heart (Vessels C and D).
- Vessel D enters the left atrium from the lungs, making it the pulmonary vein.
Question 05.5: Structure of an Artery Wall
1 Mark • Assessment Objective: AO1
✅ Mark Scheme Answer
Thick elastic / muscle layer (or thick wall containing elastic fibres and smooth muscle).
❌ Common Errors
- Writing just "thick wall" without qualifying that it contains muscle or elastic tissue (insufficient).
- Saying "thick cell walls" — animal cells never have cell walls!
- Mentioning valves (arteries do not have valves, except semilunar valves at heart exits).
Question 05.6: Efficiency of Anaerobic Respiration
2 Marks • Assessment Objective: AO1
✅ Mark Scheme Answer
- Less energy released / transferred (per molecule of glucose) [1 mark]
- Due to incomplete breakdown / incomplete oxidation of glucose (glucose is only converted to lactic acid) [1 mark]
❌ Common Errors: Forbidden Phrasing
- "Energy is made/produced/created": Violates the conservation of energy! Always use "released" or "transferred".
- "No energy is released": Anaerobic respiration does release energy, just substantially less than aerobic respiration.
Question 05.7: High Post-Exercise Oxygen Consumption
2 Marks • Assessment Objective: AO2
✅ Mark Scheme Answer
- The athlete has an oxygen debt (or lactic acid concentration is high) [1 mark]
- (Extra) oxygen is required to oxidise / break down / remove lactic acid [1 mark]
💡 Key Knowledge: Oxygen Debt
During strenuous exercise, insufficient oxygen reaches muscles, causing anaerobic respiration and lactic acid build-up. The oxygen debt is the amount of extra oxygen needed after exercise to react with the accumulated lactic acid and remove it from cells.
Question 05.8: Athlete Advantage of More Red Blood Cells
2 Marks • Assessment Objective: AO2
✅ Mark Scheme Answer
- More haemoglobin so more oxygen is carried / bound (or more oxyhaemoglobin is formed) [1 mark]
- Allows more aerobic respiration to release more energy OR prevents/delays anaerobic respiration resulting in less muscle fatigue / cramp [1 mark]
🧠 Exam Technique: The "Cause & Effect" Chain
Always build your answer logically:
More red blood cells ➔ More haemoglobin ➔ More oxygen transported ➔ More aerobic respiration ➔ More energy released / delayed fatigue .
Topics
Biology · B1: Cell Biology · B2: Organisation · B4: Bioenergetics
Question and mark scheme from the AQA GCSE Biology examination, Biology Paper 1 (Higher), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.