# Explain how the alveoli are adapted to allow efficient gas exchange in the lungs.

> Edexcel GCSE Biology (1BI0) — 8.1 Gas exchange · Explain · 4 marks

## Mark scheme (4 marks)

1. Large surface area increases the rate of diffusion / more molecules can diffuse at once
2. Thin walls reduce the diffusion distance so gases diffuse more quickly
3. Good/rich blood supply maintains a steep concentration gradient for oxygen and carbon dioxide
4. Moist lining allows gases to dissolve so they can diffuse across the exchange surface

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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/explain-how-the-alveoli-are-adapted-2dcdfdf9) · Published by Druglandscape Ltd.