Exercise 1 — IGCSE 0653 May/Jun 2023 Paper 31 Q4
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diaphragm labelled D
Cambridge IGCSE·Combined Sciences 0653·Biology
Gas Exchange Respiration
Key knowledge — Gas Exchange Respiration
Formulas & equations
Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+energy/ATP)Anaerobic respiration (animals): C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid, less energy)Anaerobic respiration (yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (ethanol + CO₂)
Key facts & rules
- Aerobic respiration releases ~38 ATP per glucose. Anaerobic releases ~2 ATP per glucose.
- Oxygen debt: extra O₂ needed after anaerobic respiration to break down lactic acid.
- Alveoli: millions in lungs; large surface area, moist, thin walls (one cell thick), rich blood supply.
- Breathing in (inhalation): diaphragm contracts and flattens, intercostal muscles raise ribs, thorax volume increases, pressure decreases.
- Breathing out (exhalation): diaphragm relaxes, ribs fall, thorax volume decreases, pressure increases.
- Trachea → bronchi → bronchioles → alveoli.
- Smoking damages cilia, causes excess mucus, destroys alveolar walls (emphysema), and increases cancer risk.
IGCSE Biology — Gas Exchange & Respiration
103 Cambridge IGCSE 0653 Combined Sciences past paper questions on gas exchange & respiration, across Theory, Multiple Choice and Alternative to Practical.
About Gas Exchange & Respiration on IGCSE 0653
Aerobic respiration releases energy from glucose using oxygen, producing carbon dioxide and water. Anaerobic respiration occurs without oxygen and releases less energy. The lungs are adapted for efficient gas exchange.
What's covered:
- Aerobic respiration: glucose + oxygen → CO₂ + water + energy
- Anaerobic respiration in animals: lactic acid
- Anaerobic respiration in yeast: ethanol + CO₂
- Lung structure: alveoli, large surface area, moist, thin walls
- Breathing mechanism
Theory
Gas Exchange & Respiration — Core7 · Paper 3
Exercise 2 — IGCSE 0653 May/Jun 2023 Paper 32 Q4
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test-tube B:
Exercise 3 — IGCSE 0653 May/Jun 2023 Paper 31 Q7
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R
Exercise 4 — IGCSE 0653 May/Jun 2023 Paper 33 Q7
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insects and marmot
Exercise 5 — IGCSE 0653 Oct/Nov 2023 Paper 32 Q1
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E
Exercise 6 — IGCSE 0653 Oct/Nov 2023 Paper 33 Q1
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E
Exercise 7 — IGCSE 0653 Oct/Nov 2023 Paper 31 Q7
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arrows from carp to heron AND from heron to alligator
Gas Exchange & Respiration — Extended3 · Paper 4
Exercise 1 — IGCSE 0653 Mar 2023 Paper 42 Q7
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A
Exercise 2 — IGCSE 0653 Oct/Nov 2023 Paper 43 Q1
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A rib
Exercise 3 — IGCSE 0653 Oct/Nov 2023 Paper 41 Q4
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intercostal muscle
Multiple choice
Gas Exchange & Respiration — Core MCQ58 · Paper 1
Question 1 — IGCSE 0653 Mar 2023 Paper 12 Q4
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Correct answer: C
Question 2 — IGCSE 0653 Mar 2023 Paper 12 Q5
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Correct answer: A
Question 3 — IGCSE 0653 Mar 2023 Paper 12 Q6
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Correct answer: D
Question 4 — IGCSE 0653 Mar 2023 Paper 12 Q7
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Correct answer: D
Question 5 — IGCSE 0653 Mar 2024 Paper 12 Q12
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Correct answer: A
Question 6 — IGCSE 0653 Mar 2024 Paper 12 Q13
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Correct answer: B
Question 7 — IGCSE 0653 Mar 2024 Paper 12 Q14
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Correct answer: C
Question 8 — IGCSE 0653 Mar 2024 Paper 12 Q15
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Correct answer: B
Question 9 — IGCSE 0653 Mar 2025 Paper 12 Q1
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Correct answer: C
Question 10 — IGCSE 0653 Mar 2025 Paper 12 Q2
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Correct answer: D
Question 11 — IGCSE 0653 Mar 2025 Paper 12 Q3
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Correct answer: C
Question 12 — IGCSE 0653 Mar 2025 Paper 12 Q4
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Correct answer: B
Question 13 — IGCSE 0653 Mar 2025 Paper 12 Q6
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Correct answer: A
Question 14 — IGCSE 0653 Mar 2025 Paper 12 Q7
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Correct answer: D
Question 15 — IGCSE 0653 May/Jun 2023 Paper 12 Q4
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Correct answer: D
Question 16 — IGCSE 0653 May/Jun 2023 Paper 12 Q5
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Correct answer: C
Question 17 — IGCSE 0653 May/Jun 2023 Paper 11 Q6
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Correct answer: D
Question 18 — IGCSE 0653 May/Jun 2023 Paper 12 Q6
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Correct answer: C
Question 19 — IGCSE 0653 May/Jun 2023 Paper 11 Q7
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Correct answer: B
Question 20 — IGCSE 0653 May/Jun 2023 Paper 11 Q8
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Correct answer: A
Question 21 — IGCSE 0653 May/Jun 2023 Paper 13 Q13
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Correct answer: A
Question 22 — IGCSE 0653 May/Jun 2023 Paper 13 Q14
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Correct answer: C
Question 23 — IGCSE 0653 May/Jun 2023 Paper 13 Q15
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Correct answer: C
Question 24 — IGCSE 0653 May/Jun 2024 Paper 13 Q1
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Correct answer: C
Question 25 — IGCSE 0653 May/Jun 2024 Paper 13 Q2
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Correct answer: A
Question 26 — IGCSE 0653 May/Jun 2024 Paper 13 Q3
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Correct answer: B
Question 27 — IGCSE 0653 May/Jun 2024 Paper 13 Q4
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Correct answer: A
Question 28 — IGCSE 0653 May/Jun 2024 Paper 13 Q5
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Correct answer: B
Question 29 — IGCSE 0653 May/Jun 2024 Paper 12 Q6
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Correct answer: A
Question 30 — IGCSE 0653 May/Jun 2024 Paper 13 Q6
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Correct answer: B
Question 31 — IGCSE 0653 May/Jun 2024 Paper 12 Q7
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Correct answer: B
Question 32 — IGCSE 0653 May/Jun 2024 Paper 11 Q8
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Correct answer: B
Question 33 — IGCSE 0653 May/Jun 2024 Paper 12 Q8
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Correct answer: B
Question 34 — IGCSE 0653 May/Jun 2025 Paper 13 Q13
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Correct answer: B
Question 35 — IGCSE 0653 May/Jun 2025 Paper 13 Q14
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Correct answer: A
Question 36 — IGCSE 0653 May/Jun 2025 Paper 13 Q15
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Correct answer: C
Question 37 — IGCSE 0653 May/Jun 2025 Paper 13 Q16
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Correct answer: A
Question 38 — IGCSE 0653 Oct/Nov 2023 Paper 11 Q5
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Correct answer: A
Question 39 — IGCSE 0653 Oct/Nov 2023 Paper 12 Q5
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Correct answer: D
Question 40 — IGCSE 0653 Oct/Nov 2023 Paper 13 Q5
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Correct answer: D
Question 41 — IGCSE 0653 Oct/Nov 2023 Paper 11 Q6
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Correct answer: A
Question 42 — IGCSE 0653 Oct/Nov 2023 Paper 12 Q6
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Correct answer: A
Question 43 — IGCSE 0653 Oct/Nov 2023 Paper 13 Q6
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Correct answer: A
Question 44 — IGCSE 0653 Oct/Nov 2023 Paper 11 Q7
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Correct answer: A
Question 45 — IGCSE 0653 Oct/Nov 2023 Paper 12 Q7
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Correct answer: B
Question 46 — IGCSE 0653 Oct/Nov 2023 Paper 13 Q7
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Correct answer: B
Question 47 — IGCSE 0653 Oct/Nov 2023 Paper 11 Q12
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Correct answer: D
Question 48 — IGCSE 0653 Oct/Nov 2023 Paper 11 Q13
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Correct answer: C
Question 49 — IGCSE 0653 Oct/Nov 2023 Paper 12 Q13
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Correct answer: A
Question 50 — IGCSE 0653 Oct/Nov 2023 Paper 13 Q13
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Correct answer: A
Question 51 — IGCSE 0653 Oct/Nov 2023 Paper 11 Q14
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Correct answer: B
Question 52 — IGCSE 0653 Oct/Nov 2023 Paper 12 Q14
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Correct answer: C
Question 53 — IGCSE 0653 Oct/Nov 2023 Paper 13 Q14
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Correct answer: C
Question 54 — IGCSE 0653 Oct/Nov 2023 Paper 11 Q15
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Correct answer: C
Question 55 — IGCSE 0653 Oct/Nov 2023 Paper 12 Q15
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Correct answer: D
Question 56 — IGCSE 0653 Oct/Nov 2023 Paper 13 Q15
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Correct answer: D
Question 57 — IGCSE 0653 Oct/Nov 2023 Paper 12 Q16
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Correct answer: B
Question 58 — IGCSE 0653 Oct/Nov 2023 Paper 13 Q16
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Correct answer: B
Gas Exchange & Respiration — Extended MCQ33 · Paper 2
Question 1 — IGCSE 0653 Mar 2023 Paper 22 Q13
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Correct answer: C
Question 2 — IGCSE 0653 Mar 2023 Paper 22 Q14
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Correct answer: D
Question 3 — IGCSE 0653 Mar 2023 Paper 22 Q15
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Correct answer: A
Question 4 — IGCSE 0653 Mar 2025 Paper 22 Q6
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Correct answer: B
Question 5 — IGCSE 0653 Mar 2025 Paper 22 Q7
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Correct answer: A
Question 6 — IGCSE 0653 Mar 2025 Paper 22 Q8
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Correct answer: D
Question 7 — IGCSE 0653 May/Jun 2023 Paper 21 Q11
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Correct answer: B
Question 8 — IGCSE 0653 May/Jun 2023 Paper 21 Q12
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Correct answer: C
Question 9 — IGCSE 0653 May/Jun 2023 Paper 22 Q12
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Correct answer: D
Question 10 — IGCSE 0653 May/Jun 2023 Paper 23 Q12
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Correct answer: D
Question 11 — IGCSE 0653 May/Jun 2023 Paper 21 Q13
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Correct answer: A
Question 12 — IGCSE 0653 May/Jun 2023 Paper 22 Q13
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Correct answer: B
Question 13 — IGCSE 0653 May/Jun 2023 Paper 23 Q13
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Correct answer: B
Question 14 — IGCSE 0653 May/Jun 2024 Paper 21 Q3
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Correct answer: B
Question 15 — IGCSE 0653 May/Jun 2024 Paper 23 Q3
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Correct answer: D
Question 16 — IGCSE 0653 May/Jun 2024 Paper 21 Q4
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Correct answer: A
Question 17 — IGCSE 0653 May/Jun 2024 Paper 22 Q4
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Correct answer: C
Question 18 — IGCSE 0653 May/Jun 2024 Paper 23 Q4
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Correct answer: A
Question 19 — IGCSE 0653 May/Jun 2024 Paper 21 Q5
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Correct answer: B
Question 20 — IGCSE 0653 May/Jun 2024 Paper 22 Q5
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Correct answer: A
Question 21 — IGCSE 0653 May/Jun 2024 Paper 23 Q5
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Correct answer: B
Question 22 — IGCSE 0653 May/Jun 2024 Paper 21 Q6
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Correct answer: C
Question 23 — IGCSE 0653 May/Jun 2024 Paper 22 Q6
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Correct answer: B
Question 24 — IGCSE 0653 May/Jun 2024 Paper 22 Q7
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Correct answer: C
Question 25 — IGCSE 0653 May/Jun 2025 Paper 22 Q10
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Correct answer: A
Question 26 — IGCSE 0653 May/Jun 2025 Paper 22 Q11
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Correct answer: D
Question 27 — IGCSE 0653 May/Jun 2025 Paper 22 Q12
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Correct answer: A
Question 28 — IGCSE 0653 Oct/Nov 2023 Paper 22 Q4
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Correct answer: A
Question 29 — IGCSE 0653 Oct/Nov 2023 Paper 22 Q5
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Correct answer: C
Question 30 — IGCSE 0653 Oct/Nov 2023 Paper 23 Q5
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Correct answer: A
Question 31 — IGCSE 0653 Oct/Nov 2023 Paper 22 Q6
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Correct answer: D
Question 32 — IGCSE 0653 Oct/Nov 2023 Paper 23 Q6
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Correct answer: C
Question 33 — IGCSE 0653 Oct/Nov 2023 Paper 23 Q7
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Correct answer: B
Alternative to practical
Gas Exchange & Respiration — ATP2 questions
Exercise 1 — IGCSE 0653 May/Jun 2024 Paper 63 Q1
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348
Exercise 2 — IGCSE 0653 May/Jun 2024 Paper 63 Q2
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One marking point from each section and any two other marking points:
All Gas Exchange & Respiration questions in this collection
| Type | Level | Paper | Session | Q# | Marks | Answer / key |
|---|---|---|---|---|---|---|
| ATP | Extended | Paper 63 | May/Jun 2024 | Q1 | 7 marks | 348 |
| ATP | Extended | Paper 63 | May/Jun 2024 | Q2 | 7 marks | One marking point from each section and any two other marking points: |
| MCQ | Core | Paper 12 | Mar 2023 | Q4 | 1 mark | C |
| MCQ | Core | Paper 12 | Mar 2023 | Q5 | 1 mark | A |
| MCQ | Core | Paper 12 | Mar 2023 | Q6 | 1 mark | D |
| MCQ | Core | Paper 12 | Mar 2023 | Q7 | 1 mark | D |
| MCQ | Core | Paper 12 | Mar 2024 | Q12 | 1 mark | A |
| MCQ | Core | Paper 12 | Mar 2024 | Q13 | 1 mark | B |
| MCQ | Core | Paper 12 | Mar 2024 | Q14 | 1 mark | C |
| MCQ | Core | Paper 12 | Mar 2024 | Q15 | 1 mark | B |
| MCQ | Core | Paper 12 | Mar 2025 | Q1 | 1 mark | C |
| MCQ | Core | Paper 12 | Mar 2025 | Q2 | 1 mark | D |
| MCQ | Core | Paper 12 | Mar 2025 | Q3 | 1 mark | C |
| MCQ | Core | Paper 12 | Mar 2025 | Q4 | 1 mark | B |
| MCQ | Core | Paper 12 | Mar 2025 | Q6 | 1 mark | A |
| MCQ | Core | Paper 12 | Mar 2025 | Q7 | 1 mark | D |
| MCQ | Core | Paper 12 | May/Jun 2023 | Q4 | 1 mark | D |
| MCQ | Core | Paper 12 | May/Jun 2023 | Q5 | 1 mark | C |
| MCQ | Core | Paper 11 | May/Jun 2023 | Q6 | 1 mark | D |
| MCQ | Core | Paper 12 | May/Jun 2023 | Q6 | 1 mark | C |
| MCQ | Core | Paper 11 | May/Jun 2023 | Q7 | 1 mark | B |
| MCQ | Core | Paper 11 | May/Jun 2023 | Q8 | 1 mark | A |
| MCQ | Core | Paper 13 | May/Jun 2023 | Q13 | 1 mark | A |
| MCQ | Core | Paper 13 | May/Jun 2023 | Q14 | 1 mark | C |
| MCQ | Core | Paper 13 | May/Jun 2023 | Q15 | 1 mark | C |
| MCQ | Core | Paper 13 | May/Jun 2024 | Q1 | 1 mark | C |
| MCQ | Core | Paper 13 | May/Jun 2024 | Q2 | 1 mark | A |
| MCQ | Core | Paper 13 | May/Jun 2024 | Q3 | 1 mark | B |
| MCQ | Core | Paper 13 | May/Jun 2024 | Q4 | 1 mark | A |
| MCQ | Core | Paper 13 | May/Jun 2024 | Q5 | 1 mark | B |
| MCQ | Core | Paper 12 | May/Jun 2024 | Q6 | 1 mark | A |
| MCQ | Core | Paper 13 | May/Jun 2024 | Q6 | 1 mark | B |
| MCQ | Core | Paper 12 | May/Jun 2024 | Q7 | 1 mark | B |
| MCQ | Core | Paper 11 | May/Jun 2024 | Q8 | 1 mark | B |
| MCQ | Core | Paper 12 | May/Jun 2024 | Q8 | 1 mark | B |
| MCQ | Core | Paper 13 | May/Jun 2025 | Q13 | 1 mark | B |
| MCQ | Core | Paper 13 | May/Jun 2025 | Q14 | 1 mark | A |
| MCQ | Core | Paper 13 | May/Jun 2025 | Q15 | 1 mark | C |
| MCQ | Core | Paper 13 | May/Jun 2025 | Q16 | 1 mark | A |
| MCQ | Core | Paper 11 | Oct/Nov 2023 | Q5 | 1 mark | A |
| MCQ | Core | Paper 12 | Oct/Nov 2023 | Q5 | 1 mark | D |
| MCQ | Core | Paper 13 | Oct/Nov 2023 | Q5 | 1 mark | D |
| MCQ | Core | Paper 11 | Oct/Nov 2023 | Q6 | 1 mark | A |
| MCQ | Core | Paper 12 | Oct/Nov 2023 | Q6 | 1 mark | A |
| MCQ | Core | Paper 13 | Oct/Nov 2023 | Q6 | 1 mark | A |
| MCQ | Core | Paper 11 | Oct/Nov 2023 | Q7 | 1 mark | A |
| MCQ | Core | Paper 12 | Oct/Nov 2023 | Q7 | 1 mark | B |
| MCQ | Core | Paper 13 | Oct/Nov 2023 | Q7 | 1 mark | B |
| MCQ | Core | Paper 11 | Oct/Nov 2023 | Q12 | 1 mark | D |
| MCQ | Core | Paper 11 | Oct/Nov 2023 | Q13 | 1 mark | C |
| MCQ | Core | Paper 12 | Oct/Nov 2023 | Q13 | 1 mark | A |
| MCQ | Core | Paper 13 | Oct/Nov 2023 | Q13 | 1 mark | A |
| MCQ | Core | Paper 11 | Oct/Nov 2023 | Q14 | 1 mark | B |
| MCQ | Core | Paper 12 | Oct/Nov 2023 | Q14 | 1 mark | C |
| MCQ | Core | Paper 13 | Oct/Nov 2023 | Q14 | 1 mark | C |
| MCQ | Core | Paper 11 | Oct/Nov 2023 | Q15 | 1 mark | C |
| MCQ | Core | Paper 12 | Oct/Nov 2023 | Q15 | 1 mark | D |
| MCQ | Core | Paper 13 | Oct/Nov 2023 | Q15 | 1 mark | D |
| MCQ | Core | Paper 12 | Oct/Nov 2023 | Q16 | 1 mark | B |
| MCQ | Core | Paper 13 | Oct/Nov 2023 | Q16 | 1 mark | B |
| MCQ | Extended | Paper 22 | Mar 2023 | Q13 | 1 mark | C |
| MCQ | Extended | Paper 22 | Mar 2023 | Q14 | 1 mark | D |
| MCQ | Extended | Paper 22 | Mar 2023 | Q15 | 1 mark | A |
| MCQ | Extended | Paper 22 | Mar 2025 | Q6 | 1 mark | B |
| MCQ | Extended | Paper 22 | Mar 2025 | Q7 | 1 mark | A |
| MCQ | Extended | Paper 22 | Mar 2025 | Q8 | 1 mark | D |
| MCQ | Extended | Paper 21 | May/Jun 2023 | Q11 | 1 mark | B |
| MCQ | Extended | Paper 21 | May/Jun 2023 | Q12 | 1 mark | C |
| MCQ | Extended | Paper 22 | May/Jun 2023 | Q12 | 1 mark | D |
| MCQ | Extended | Paper 23 | May/Jun 2023 | Q12 | 1 mark | D |
| MCQ | Extended | Paper 21 | May/Jun 2023 | Q13 | 1 mark | A |
| MCQ | Extended | Paper 22 | May/Jun 2023 | Q13 | 1 mark | B |
| MCQ | Extended | Paper 23 | May/Jun 2023 | Q13 | 1 mark | B |
| MCQ | Extended | Paper 21 | May/Jun 2024 | Q3 | 1 mark | B |
| MCQ | Extended | Paper 23 | May/Jun 2024 | Q3 | 1 mark | D |
| MCQ | Extended | Paper 21 | May/Jun 2024 | Q4 | 1 mark | A |
| MCQ | Extended | Paper 22 | May/Jun 2024 | Q4 | 1 mark | C |
| MCQ | Extended | Paper 23 | May/Jun 2024 | Q4 | 1 mark | A |
| MCQ | Extended | Paper 21 | May/Jun 2024 | Q5 | 1 mark | B |
| MCQ | Extended | Paper 22 | May/Jun 2024 | Q5 | 1 mark | A |
| MCQ | Extended | Paper 23 | May/Jun 2024 | Q5 | 1 mark | B |
| MCQ | Extended | Paper 21 | May/Jun 2024 | Q6 | 1 mark | C |
| MCQ | Extended | Paper 22 | May/Jun 2024 | Q6 | 1 mark | B |
| MCQ | Extended | Paper 22 | May/Jun 2024 | Q7 | 1 mark | C |
| MCQ | Extended | Paper 22 | May/Jun 2025 | Q10 | 1 mark | A |
| MCQ | Extended | Paper 22 | May/Jun 2025 | Q11 | 1 mark | D |
| MCQ | Extended | Paper 22 | May/Jun 2025 | Q12 | 1 mark | A |
| MCQ | Extended | Paper 22 | Oct/Nov 2023 | Q4 | 1 mark | A |
| MCQ | Extended | Paper 22 | Oct/Nov 2023 | Q5 | 1 mark | C |
| MCQ | Extended | Paper 23 | Oct/Nov 2023 | Q5 | 1 mark | A |
| MCQ | Extended | Paper 22 | Oct/Nov 2023 | Q6 | 1 mark | D |
| MCQ | Extended | Paper 23 | Oct/Nov 2023 | Q6 | 1 mark | C |
| MCQ | Extended | Paper 23 | Oct/Nov 2023 | Q7 | 1 mark | B |
| Theory | Core | Paper 31 | May/Jun 2023 | Q4 | 9 marks | diaphragm labelled D |
| Theory | Core | Paper 32 | May/Jun 2023 | Q4 | 9 marks | test-tube B: |
| Theory | Core | Paper 31 | May/Jun 2023 | Q7 | 10 marks | R |
| Theory | Core | Paper 33 | May/Jun 2023 | Q7 | 8 marks | insects and marmot |
| Theory | Core | Paper 32 | Oct/Nov 2023 | Q1 | 10 marks | E |
| Theory | Core | Paper 33 | Oct/Nov 2023 | Q1 | 10 marks | E |
| Theory | Core | Paper 31 | Oct/Nov 2023 | Q7 | 9 marks | arrows from carp to heron AND from heron to alligator |
| Theory | Extended | Paper 42 | Mar 2023 | Q7 | 7 marks | A |
| Theory | Extended | Paper 43 | Oct/Nov 2023 | Q1 | 10 marks | A rib |
| Theory | Extended | Paper 41 | Oct/Nov 2023 | Q4 | 7 marks | intercostal muscle |