# Explain how the structure of red blood cells makes them well adapted for transporting oxygen in the blood.

> Pearson Edexcel A-Level Biology A (9BI0) — 1.3 Mass transport in animals · Explain · 5 marks

## Mark scheme (5 marks)

1. Red blood cells have a biconcave disc shape
2. This gives a large surface area to volume ratio, allowing more oxygen to diffuse in and out quickly
3. Red blood cells contain haemoglobin, which binds to oxygen
4. Red blood cells have no nucleus, leaving more space/volume for haemoglobin
5. Their small size and flexible shape allows them to squeeze through narrow capillaries to deliver oxygen to tissues

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-red-2b100e64) · Published by Druglandscape Ltd.