# Explain how the structure of red blood cells makes them well suited to carrying oxygen around the body.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 1.3 Mass transport in animals · Explain · 5 marks

> Red blood cells are specialised cells that transport oxygen from the lungs to respiring tissues. They are found in large numbers in the blood and have several structural adaptations.

## Mark scheme (5 marks)

1. Red blood cells have a biconcave disc shape
2. This increases the surface area to volume ratio, allowing faster diffusion of oxygen into/out of the cell
3. Red blood cells contain haemoglobin, which binds to oxygen to form oxyhaemoglobin
4. Red blood cells have no nucleus, leaving more space for haemoglobin / allowing more oxygen to be carried
5. Oxyhaemoglobin releases oxygen at respiring tissues, allowing cells to carry out aerobic respiration

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-red-2b214679) · Published by Druglandscape Ltd.