# A child is born with a condition called anaemia, in which their blood contains fewer red blood cells than normal. Explain how this condition affects the transport of oxygen around the body, referring to the roles of the heart and blood vessels in the double circulatory system.

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

> Anaemia is a condition in which a person has fewer red blood cells than normal. Doctors find that the child's tissues are not receiving enough oxygen, even though the heart is beating normally.

## Mark scheme (5 marks)

1. Red blood cells carry oxygen around the body
2. Fewer red blood cells means less oxygen is transported to the body's tissues
3. The heart pumps oxygenated blood from the lungs to the body via the aorta / arteries carry blood away from the heart under high pressure
4. In the double circulatory system, blood passes through the heart twice in one full circuit — once to the lungs and once to the body
5. Because there are fewer red blood cells, less oxygen is collected at the lungs and so less oxygen is delivered to tissues, causing symptoms of anaemia

## Key terms

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

## 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-child-is-born-with-a-bcbbbfc0) · Published by Druglandscape Ltd.