# A diver surfaces too quickly from a deep-sea dive. Paramedics suspect the diver's blood is not delivering enough oxygen to the body's tissues. Explain how the structure of red blood cells and the role of plasma make blood an efficient transport tissue.

> OCR A-Level Biology B — Advancing Biology (H422) — 2.5 Cardiovascular system · Explain · 5 marks

> Blood is a tissue that contains red blood cells, white blood cells, plasma and platelets. Red blood cells are biconcave in shape and carry oxygen around the body. Plasma transports many dissolved substances, including nutrients, urea and hormones.

## Mark scheme (5 marks)

1. Red blood cells are biconcave in shape
2. The biconcave shape increases surface area (for gaseous exchange / oxygen absorption)
3. Red blood cells carry/transport oxygen (to the body's tissues)
4. Plasma is a pale yellow liquid that transports dissolved substances such as nutrients, urea, hormones or salts (any one valid example accepted)
5. Together red blood cells and plasma allow blood to transport both gases and dissolved substances, making it an efficient transport tissue (idea of combined/dual role)

## Key terms

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

## Related

- [Revision notes for OCR A-Level Biology B — Advancing Biology (H422)](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/a-diver-surfaces-too-quickly-from-cd951638) · Published by Druglandscape Ltd.