Q1. [2] medium exam-ready
Muscle cramps in athletes often occur during intense exercise. Explain the biochemical reason for this.
Generated by claude-sonnet-4-6 · 2026-06-26 00:59 · grounding rag
Model Answer
During intense exercise, the body's demand for energy is high, but oxygen supply becomes insufficient. The muscle cells then respire anaerobically, breaking down glucose to produce energy and lactic acid. Accumulation of lactic acid in the muscles causes muscle cramps in athletes.
Explanation
- The key concept here is anaerobic respiration in muscle cells: Glucose → Lactic acid + Energy.
- Examiners want two points: (1) insufficient oxygen during intense exercise leads to anaerobic respiration, and (2) lactic acid build-up causes cramps.
- This is from the chapter on Life Processes (Chapter 6, respiration). Avoid writing about aerobic respiration in detail — just contrast it briefly to show why anaerobic pathway is used.
- Remember: in yeast, anaerobic respiration produces ethanol + CO₂; in muscles, it produces lactic acid — this distinction is commonly tested.