Explain how the structure of an enzyme allows it to carry out its specific function, and describe what happens to the enzyme when it is exposed to a very high temperature.

WJEC A-Level Biology (Wales) — 1.2 Cell structure and organisation · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

An enzyme has a specific active site that is shaped to fit its substrate.
The active site is complementary to the substrate, so the enzyme and substrate form an enzyme‑substrate complex.
When the enzyme is exposed to a very high temperature it denatures.
Denaturation changes the shape of the active site, so the substrate can no longer fit and no enzyme‑substrate complexes can form.

Examiner tips

  • Use the term "active site" and explain its specific shape and complementarity. Show the sequence: active site → enzyme‑substrate complex → denaturation. Mention that denaturation is caused by high temperature and leads to loss of function.

Common mistakes

  • Forgetting to mention the active site’s specific shape. Saying the enzyme is "destroyed" instead of "denatures". Not linking denaturation to loss of enzyme‑substrate complex formation.

Mark scheme (5 marks)

  1. The enzyme has an active site with a specific shape
  2. The active site is complementary to the substrate
  3. An enzyme-substrate complex is formed
  4. At very high temperatures the enzyme denatures
  5. The shape of the active site changes so the substrate can no longer fit / no enzyme-substrate complexes can form

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