AQA GCSE Biology

Digestion & enzymes

AQA GCSE Biology revision on Digestion & enzymes. 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

    Which enzyme digests proteins?

    • A) Amylase
    • B) Protease
    • C) Lipase
    • D) Catalase
    Show answer

    Answer: Protease

    Three main digestive enzymes: amylase (carbohydrate -> simple sugars), protease (protein -> amino acids), lipase (lipids -> fatty acids + glycerol). Each is specific to one substrate.

  2. Question 2

    At which pH does the enzyme pepsin (in the stomach) work best?

    • A) pH 2 (acidic)
    • B) pH 7 (neutral)
    • C) pH 9 (alkaline)
    • D) pH 12 (strongly alkaline)
    Show answer

    Answer: pH 2 (acidic)

    Pepsin is a protease in the stomach. The stomach contains hydrochloric acid (pH ~2), which is pepsin's optimum. At neutral pH the enzyme is denatured (active site changes shape and substrate no longer fits).

  3. Question 3

    Bile is produced in the ___ and stored in the ___.

    • A) pancreas; stomach
    • B) liver; gall bladder
    • C) kidney; liver
    • D) stomach; intestine
    Show answer

    Answer: liver; gall bladder

    Bile has two jobs: (1) it's alkaline, neutralising acidic chyme from the stomach so intestinal enzymes work properly. (2) It EMULSIFIES fats - breaks big fat droplets into many small ones, hugely increasing surface area for lipase to act on. Speeds up fat digestion massively.

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