Practise 43 real questions on Gas exchange and respiration from 2021 to 2026. See the answer and explanation as soon as you answer.
Gas exchange and respiration is one of the 13 main topics in our O Level Biology (Cambridge (CAIE) 5090) question bank, and about 7% of its real questions come from it. Tayyari Karo has 43 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2, Paper 3, Paper 4; 28 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 30 medium, 7 hard, 6 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
Which equation shows the type of respiration that can cause an 'oxygen debt' in muscles during vigorous exercise?
Answer: D. glucose -> lactic acid
Anaerobic respiration in muscle produces lactic acid, which needs oxygen to remove afterwards (oxygen debt).
Which sets of muscles contract to cause the body to breathe in?
Answer: A. diaphragm and external intercostal muscles
Which equation represents anaerobic respiration in humans?
Answer: C. glucose → lactic acid
Human anaerobic respiration: glucose → lactic acid.
Which equation shows the type of respiration that can cause an 'oxygen debt' in muscles during vigorous exercise?
Answer: B. glucose → lactic acid
Anaerobic respiration in muscles produces lactic acid, causing oxygen debt.
An experiment is set up with limewater in test-tubes 1 and 2; air is pumped through, passing a solution that absorbs carbon dioxide, then living animals. What is the appearance of the limewater in test-tubes 1 and 2 after 10 minutes?
Answer: B. clear / cloudy
In an investigation, scientists treated plant roots with a chemical that stops aerobic respiration. They observed that after the treatment the plant roots absorbed nitrate ions more slowly. Which statement explains this observation?
Answer: C. There is less energy for active transport of nitrate ions.
A root hair cell respires aerobically. (a)(i) Name the structures within the cell that carry out aerobic respiration. [1] (a)(ii) Write the balanced symbol equation for aerobic respiration of glucose. [2] (b) State a weather condition that may lead to a root hair cell respiring anaerobically and explain. [2]
(a)(i) Mitochondria. (a)(ii) C6H12O6 + 6O2 -> 6CO2 + 6H2O. (b) Waterlogging (heavy rain) - reduces oxygen in soil so roots respire anaerobically (producing ethanol/lactic acid). Low humidity/high temperature increases transpiration/water loss also affecting.
Model answers; verify with 5090_w23_ms_21.
The forelimb of a lion has the same basic structure as the human arm (bones X, Y, ulna). (a) State the name of bone X and the muscle between bones X and Y. [2] (b)(i) Name the process used to release energy in the muscles when the lion starts to run. [1] (b)(ii) Explain why the lion can only run at maximum speed for a short time. [2]
(a) Bone X = humerus; muscle between X and Y = biceps (or triceps). (b)(i) Respiration (aerobic and then anaerobic). (b)(ii) Anaerobic respiration builds up lactic acid and oxygen debt; muscles tire, so it can only sustain max speed briefly before needing recovery.
Model answers; verify with 5090_w22_ms_21.
| Session | Paper 1 | Paper 2 | Paper 3 | Paper 4 |
|---|---|---|---|---|
| May/June 2026 | 1 | 2 | – | – |
| May/June 2025 | 2 | – | – | – |
| Oct/Nov 2025 | 3 | – | 1 | 1 |
| May/June 2024 | 2 | 1 | – | 1 |
| Oct/Nov 2024 | 1 | – | 2 | 2 |
| May/June 2023 | 3 | – | – | – |
| Oct/Nov 2023 | 3 | 1 | – | – |
| May/June 2022 | 4 | 1 | – | – |
| Oct/Nov 2022 | 3 | 1 | – | – |
| May/June 2021 | 3 | 1 | – | – |
| Oct/Nov 2021 | 3 | 1 | – | – |
43 real O Level Biology (5090) questions on Gas exchange and respiration from 2021 to 2026, from Paper 1, Paper 2, Paper 3, Paper 4. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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