AQA GCSE Biology

Enzymes & lock-and-key

AQA GCSE Biology revision on Enzymes & lock-and-key. 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 specific part of an enzyme molecule must be complementary to the shape of the substrate?

    • A) The active site
    • B) The globular tail
    • C) The peptide region
    • D) The amino segment
    Show answer

    Answer: The active site

    Enzymes are proteins with a unique 3D shape created by folding. The active site is a specific depression or cleft that matches the substrate's shape, allowing them to fit together like a lock and key.

  2. Question 2

    What happens to the enzyme-substrate complex once the chemical reaction has been successfully completed?

    • A) The enzyme is consumed
    • B) The product is released
    • C) The site is deactivated
    • D) The protein is modified
    Show answer

    Answer: The product is released

    Enzymes act as biological catalysts, meaning they facilitate reactions without being used up. Once the substrate is converted into products, the products no longer fit the active site and are released, leaving the enzyme ready to bind a new substrate molecule.

  3. Question 3

    What term describes the state of an enzyme when its active site shape is permanently altered by extreme heat?

    Show answer

    Answer: denatured

    Enzymes are proteins held together by weak bonds. High temperatures provide enough energy to break these bonds, causing the protein structure to unfold. Once the active site is no longer the correct shape, it can no longer bind to its specific substrate.

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