AQA GCSE Biology

Respiration

AQA GCSE Biology revision on Respiration. Aligned to the AQA GCSE Biology 8461 specification. This bank has 25 practice questions on this topic.

Sample questions (3 of 25)

  1. Question 1

    What is the equation for aerobic respiration?

    • A) Glucose + oxygen -> carbon dioxide + water
    • B) Carbon dioxide + water -> glucose + oxygen
    • C) Glucose -> lactic acid (+ energy)
    • D) Oxygen -> carbon dioxide (+ energy)
    Show answer

    Answer: Glucose + oxygen -> carbon dioxide + water

    Aerobic = with oxygen. Happens mostly in mitochondria. Releases far more energy per glucose than anaerobic respiration. Anaerobic respiration in animals produces lactic acid; in yeast it produces ethanol + CO2 (fermentation).

  2. Question 2

    Anaerobic respiration in human muscles produces...

    • A) Ethanol + CO2
    • B) Lactic acid
    • C) Pure oxygen
    • D) Water + sugar
    Show answer

    Answer: Lactic acid

    When muscles work too hard for oxygen supply to keep up (e.g. sprinting), they do anaerobic respiration. Glucose -> lactic acid + a small amount of energy. The lactic acid builds up causing fatigue + cramp. After exercise, you keep breathing hard ('oxygen debt') to break down the lactic acid in the liver.

  3. Question 3

    Anaerobic respiration in yeast is also called...

    • A) Fermentation
    • B) Photosynthesis
    • C) Digestion
    • D) Transpiration
    Show answer

    Answer: Fermentation

    Yeast (a single-celled fungus) does anaerobic respiration when oxygen is low: glucose -> ethanol + CO2 + a little energy. Used commercially: BREWING (the ethanol is the alcohol in beer + wine), BREADMAKING (CO2 bubbles make bread rise; the heat of baking evaporates the ethanol). Different products from animal anaerobic respiration (which makes lactic acid).

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