Muscle cells require large amounts of energy during exercise. Explain how ATP provides energy for muscle contraction, including how ATP is regenerated so that muscle contraction can continue.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
During intense exercise, the rate of ATP usage in muscle cells increases dramatically. Muscle cells must continuously regenerate ATP to sustain contraction.
Model answer (5 marks)
ATP is hydrolysed to ADP + Pi, releasing energy that is used directly to power the cross‑bridge cycle in muscle contraction.
During contraction the myosin head binds actin and, using the energy from ATP hydrolysis, changes shape to pull the actin filament, shortening the sarcomere.
To keep the contraction going, ATP must be regenerated. ADP and Pi are re‑combined to form ATP.
This synthesis is driven by the energy released during cellular respiration (glycolysis, the citric acid cycle and oxidative phosphorylation).
Thus, continuous ATP hydrolysis supplies the energy for contraction, while respiration provides the energy needed to regenerate ATP from ADP and Pi.
During contraction the myosin head binds actin and, using the energy from ATP hydrolysis, changes shape to pull the actin filament, shortening the sarcomere.
To keep the contraction going, ATP must be regenerated. ADP and Pi are re‑combined to form ATP.
This synthesis is driven by the energy released during cellular respiration (glycolysis, the citric acid cycle and oxidative phosphorylation).
Thus, continuous ATP hydrolysis supplies the energy for contraction, while respiration provides the energy needed to regenerate ATP from ADP and Pi.
Examiner tips
- Use the exact terms ATP, ADP, Pi and respiration; link hydrolysis to energy release and regeneration to respiration.
- Show the cycle: hydrolysis → energy for contraction → ADP+Pi → respiration → ATP regeneration.
- Keep answer concise and directly address each point in the scheme.
Common mistakes
- Confusing ATP synthesis with ATP hydrolysis; writing that ATP is broken down to produce energy for respiration.
- Omitting the role of respiration in providing the energy for ATP regeneration.
- Using vague phrases like ‘energy is used’ without specifying muscle contraction or the cross‑bridge cycle.
Mark scheme (5 marks)
- ATP is hydrolysed (broken down) to release energy
- ATP is hydrolysed into ADP and inorganic phosphate (Pi)
- The energy released is used directly for muscle contraction (a cellular process)
- ATP is regenerated by combining ADP and inorganic phosphate (Pi)
- Energy for ATP regeneration comes from respiration
Key terms in this question
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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