# Explain how the structure of capillaries makes them well suited for the exchange of substances between the blood and the tissues.

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

## Mark scheme (4 marks)

1. Capillaries have walls that are only one cell thick / very thin walls
2. This reduces the diffusion distance so substances can move quickly between blood and tissues
3. Capillaries form a large network/are numerous, giving a large surface area for exchange
4. Substances move by diffusion down a concentration gradient between the blood and tissues

## Key terms

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

## 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-structure-of-capillaries-be58e67b) · Published by Druglandscape Ltd.