Edexcel GCSE Biology

Enzymes & lock-and-key

Edexcel GCSE Biology revision on Enzymes & lock-and-key. Aligned to the Pearson Edexcel GCSE Biology 1BI0 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 binds to the substrate to form an enzyme-substrate complex?

    • A) The globular protein
    • B) The active site area
    • C) The primary structure
    • D) The polypeptide chain
    Show answer

    Answer: The active site area

    Enzymes are globular proteins with a specific 3D shape. The active site is a uniquely shaped pocket or cleft on the enzyme surface that is complementary to the specific substrate, allowing the lock-and-key mechanism to occur.

  2. Question 2

    What term describes the condition where an enzyme's active site has permanently changed shape due to extreme heat?

    Show answer

    Answer: denatured

    High temperatures cause the chemical bonds holding the enzyme's 3D structure together to break. This alters the shape of the active site so that the substrate can no longer fit, rendering the enzyme inactive.

  3. Question 3

    Why does an enzyme become less effective when the pH deviates significantly from its optimum level?

    • A) The substrate is broken
    • B) The active site alters
    • C) The enzyme melts down
    • D) The reaction is slowed
    Show answer

    Answer: The active site alters

    Enzymes have an optimum pH where they function best. Significant changes in pH interfere with the ionic and hydrogen bonds that maintain the protein's tertiary structure, causing the active site to deform and preventing substrate binding.

Want to test yourself on the remaining cards for this topic?

22 more questions on Enzymes & lock-and-key — plus mistakes tracking and spaced repetition across the whole Biology spec.

Start a free session → Already have an account? Log in

More Edexcel Biology topics