# Explain how blood is transported from the heart to the lungs and back to the heart, and why it is important that this circulation is kept separate from the circulation to the rest of the body.

> AQA A-Level Biology (7402) — 3.3.4 Mass Transport · Explain · 5 marks

## Mark scheme (5 marks)

1. The right ventricle pumps deoxygenated blood to the lungs (via the pulmonary artery)
2. Blood picks up oxygen / becomes oxygenated at the lungs
3. Oxygenated blood returns to the left side of the heart (via the pulmonary vein / into the left atrium)
4. The two circulations are separate so that oxygenated and deoxygenated blood do not mix
5. This means oxygenated blood delivered to body tissues / organs has a high oxygen concentration, so more oxygen is available for respiration

## 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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