Explain why the mitochondria are important for aerobic respiration in muscle cells during vigorous exercise.

Pearson Edexcel International GCSE Biology (4BI1) — 2.7 Respiration · Explain · 4 marks · View as Markdown

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

During a 100-metre sprint, a runner's muscle cells require a large and rapid supply of energy. The rate of aerobic respiration in these cells increases significantly.

Model answer (4 marks)

Mitochondria are the site of aerobic respiration, where glucose is oxidised with oxygen to produce ATP.

Aerobic respiration releases large amounts of energy from glucose, which is required for muscle contraction.

During vigorous exercise, the number of mitochondria and their activity increase, allowing more glucose to be oxidised.

The greater ATP supply from aerobic respiration enables sustained muscle contraction during the sprint.

Examiner tips

  • Use the term ‘mitochondria’ as the site of aerobic respiration. Mention oxygen and glucose. Explain the link between more mitochondria and more ATP. Show how ATP powers muscle contraction.

Common mistakes

  • Confusing anaerobic with aerobic respiration. Failing to mention oxygen. Not linking ATP production to muscle contraction.

Mark scheme (4 marks)

  1. Mitochondria are the site of (aerobic) respiration
  2. Aerobic respiration releases energy from glucose (using oxygen)
  3. More mitochondria / greater mitochondrial activity means more energy can be released
  4. Energy released (from aerobic respiration) is used for muscle contraction

Key terms in this question

mitochondria · aerobic respiration

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