Aerobic respiration is affected by temperature because it is catalysed by enzymes. Explain how a rise in temperature from 20 °C to 70 °C affects the rate of aerobic respiration in a yeast cell.

Cambridge International IGCSE Biology (0610) — 12.2 Aerobic respiration · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

A rise in temperature increases the kinetic energy of the molecules, so the frequency of successful collisions between enzymes and substrates rises, which increases the rate of aerobic respiration up to the optimum temperature. Above the optimum (around 70 °C) the rate falls because the high temperature denatures the enzymes, altering the shape of the active site and preventing substrate binding.

Examiner tips

  • Mention kinetic energy and collision frequency first, then state the optimum and denaturation effect
  • Use the terms ‘optimum temperature’ and ‘denature’
  • Show the two stages: increase then decrease

Common mistakes

  • Failing to mention the optimum temperature or denaturation
  • Using vague terms like ‘hot’ instead of ‘high temperature’
  • Not linking temperature to enzyme activity

Mark scheme (4 marks)

  1. Rate of aerobic respiration increases as temperature rises (up to the optimum)
  2. Because higher temperature gives molecules / enzymes and substrates more kinetic energy, increasing the frequency of successful collisions
  3. Above the optimum temperature the rate of respiration decreases / stops
  4. Because high temperatures denature the enzymes that catalyse respiration, changing the shape of the active site so substrate cannot bind

Key terms in this question

aerobic respiration · enzyme

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