Explain why maintaining a constant internal body temperature is important for enzyme-controlled reactions in the body.

WJEC GCSE Biology (Wales) — 2.5.3 Homeostasis · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Enzymes have an optimum temperature at which they work best. If the body temperature rises above this optimum the enzyme becomes denatured or the active site changes shape, reducing activity. If the temperature falls below the optimum, enzyme activity decreases and reactions slow down. Therefore, keeping a constant internal temperature ensures enzymes operate near their optimum, allowing metabolic reactions to proceed at the correct rate.

Examiner tips

  • Use the term "optimum temperature" and explain both high and low extremes.
  • Show the link between enzyme activity and reaction rate.
  • Mention that metabolic reactions must run at a controlled rate for homeostasis.

Common mistakes

  • Confusing temperature with pH or pressure.
  • Failing to explain why a constant temperature is needed for metabolic rate control.
  • Using vague language such as "good" or "bad" instead of specific enzyme effects.

Mark scheme (4 marks)

  1. Enzymes have an optimum temperature at which they work best
  2. If temperature rises above the optimum, the enzyme becomes denatured / the active site changes shape
  3. If temperature falls below the optimum, enzyme activity decreases / reactions slow down
  4. Maintaining a constant internal temperature keeps enzymes working at or near their optimum, so metabolic reactions proceed at the correct rate

Key terms in this question

enzyme

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