# Explain the roles of inorganic ions in the contraction of muscle cells and in the transport of oxygen in the blood.

> AQA A-Level Biology (7402) — 3.1.8 Inorganic Ions · Explain · 5 marks

## Mark scheme (5 marks)

1. Calcium ions are required for muscle contraction
2. Calcium ions are released into the muscle cell (from the sarcoplasmic reticulum / during a nerve impulse) to allow contraction to occur
3. Iron ions are found in / are a component of haemoglobin
4. Iron ions bind to / carry oxygen (forming oxyhaemoglobin)
5. Without sufficient iron ions haemoglobin cannot be made / cannot carry oxygen effectively, so less oxygen is transported to respiring cells

## Key terms

- [inorganic ions](https://www.gradenine.co.uk/glossary/inorganic-ions)

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-the-roles-of-inorganic-ions-3e9aa179) · Published by Druglandscape Ltd.