# Explain how the structure of a red blood cell is adapted to carry oxygen efficiently around the body.

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

## Mark scheme (5 marks)

1. Red blood cells have a biconcave disc shape
2. Biconcave shape increases the surface area (to volume ratio) for oxygen diffusion
3. Red blood cells contain haemoglobin, which carries/binds to oxygen
4. Red blood cells have no nucleus, allowing more space for haemoglobin
5. Red blood cells are small and flexible, allowing them to pass through narrow capillaries to reach all body cells

## Key terms

- [red blood cell](https://www.gradenine.co.uk/glossary/red-blood-cell)

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-a-791cda59) · Published by Druglandscape Ltd.