# A sprinter completes a 100 m race in under 12 seconds. Describe what happens in the sprinter's muscle cells to meet the high demand for energy during the race, and state one consequence of this process occurring in the muscles.

> Eduqas GCSE Biology — 1.2.1 Aerobic and anaerobic respiration · Describe · 4 marks

## Mark scheme (4 marks)

1. Muscles respire anaerobically (during the race / when oxygen supply is insufficient)
2. Glucose is broken down (incompletely) to release energy
3. Lactic acid is produced as a product of anaerobic respiration
4. A named consequence — muscle fatigue / pain / cramp OR an oxygen debt is created (muscles need extra oxygen after the race to break down lactic acid)

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