# Describe how the structure of the alveoli makes them well suited for gas exchange.

> WJEC GCSE Biology (Wales) — 1.2.2 The respiratory system · Describe · 4 marks

## Mark scheme (4 marks)

1. Large surface area (of alveoli / many alveoli)
2. Walls are one cell thick / thin walls to give a short diffusion distance
3. Rich / dense network of capillaries surrounding the alveoli (maintains a concentration gradient)
4. Moist / damp lining (allows gases to dissolve for diffusion)

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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/describe-how-the-structure-of-the-c0011ecb) · Published by Druglandscape Ltd.