# 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

> 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.

## 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

- [mitochondria](https://www.gradenine.co.uk/glossary/mitochondria)
- [aerobic respiration](https://www.gradenine.co.uk/glossary/aerobic-respiration)

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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