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IGCSEBiology
Trial Class

Original practice · 5 questions · 14 marks · about 16 minutes

Anaerobic Respiration Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your knowledge of anaerobic respiration: what happens when cells respire without oxygen.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 4 Both 3 marks Difficulty 3/5

    Write the word equation for anaerobic respiration in (a) humans and (b) yeast.

    Show model answer and marking guidance
    1. (a) In humans: glucose → lactic acid (+ small amount of energy).
    2. (b) In yeast: glucose → ethanol + carbon dioxide (+ small amount of energy).
    3. Both occur without oxygen.

  2. Question 2

    Paper 4 Extended 3 marks Difficulty 4/5

    Explain why anaerobic respiration releases less energy than aerobic respiration.

    Show model answer and marking guidance
    1. Glucose is not fully broken down: lactic acid (or ethanol) still contains chemical energy.
    2. In aerobic respiration, glucose is completely broken down to CO₂ and H₂O, releasing all the energy.
    3. Anaerobic respiration releases approximately 1/19th of the energy compared to aerobic.

  3. Question 3

    Paper 4 Both 3 marks Difficulty 3/5

    During a sprint, a runner's muscles switch to anaerobic respiration. Explain why and describe the effect on the muscles.

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    1. Oxygen cannot be supplied fast enough for aerobic respiration during intense exercise.
    2. Muscles switch to anaerobic respiration to continue releasing energy.
    3. Lactic acid builds up in the muscles, causing fatigue / cramp / pain.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 2/5

    State one use of anaerobic respiration in yeast by humans.

    Show model answer and marking guidance
    1. Brewing / making alcoholic drinks: yeast produces ethanol.
    2. Bread-making: yeast produces CO₂ which makes dough rise.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    Define "oxygen debt" and explain how it is repaid after exercise.

    Show model answer and marking guidance
    1. Oxygen debt is the extra oxygen needed after exercise to break down the lactic acid that accumulated.
    2. After exercise, breathing rate stays elevated to take in more oxygen.
    3. Lactic acid is transported to the liver where it is broken down (using oxygen) into CO₂ and water.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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