# During a weightlifting competition, an athlete repeatedly lifts heavy barbells overhead. Each lift requires muscles to contract powerfully. Explain the role of ATP, actin, myosin and calcium ions in bringing about a single muscle contraction.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.2 Muscle contraction · Explain · 5 marks

> During a weightlifting competition, an athlete repeatedly lifts heavy barbells overhead. Each lift requires the muscles to contract powerfully and rapidly.

## Mark scheme (5 marks)

1. ATP provides the energy needed for muscle contraction
2. Calcium ions are released (from the sarcoplasmic reticulum) when a nerve impulse arrives, triggering contraction
3. Myosin heads bind to binding sites on actin filaments, forming cross-bridges
4. Myosin heads pivot / pull the actin filaments towards the centre of the sarcomere (power stroke), causing the filaments to slide
5. ATP allows the myosin head to detach from actin and reset, so the cycle can repeat

## Key terms

- [ATP](https://www.gradenine.co.uk/glossary/atp)
- [actin](https://www.gradenine.co.uk/glossary/actin)
- [myosin](https://www.gradenine.co.uk/glossary/myosin)
- [calcium ions](https://www.gradenine.co.uk/glossary/calcium-ions)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/during-a-weightlifting-competition-an-athlete-4a9e44d4) · Published by Druglandscape Ltd.