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

> OCR GCSE Biology A: Gateway Science (J247) — B2.2 The challenges of size · Explain · 4 marks

> Red blood cells are specialised cells found in the blood. They are produced in the bone marrow and travel through the circulatory system delivering oxygen to respiring tissues.

## Mark scheme (4 marks)

1. Red blood cells have a biconcave shape
2. This increases the surface area (for gaseous exchange / diffusion of oxygen)
3. Red blood cells have no nucleus
4. Having no nucleus leaves more space / room for haemoglobin (to carry oxygen)

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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