# A biology teacher explains to a class that carbon dioxide and urea are both waste products that must be removed from the body, but they are excreted by different organs. Explain how carbon dioxide and urea are each produced in the body and state which organ is responsible for excreting each waste product.

> OCR A-Level Biology B — Advancing Biology (H422) — 5.6 Excretion · Explain · 5 marks

> Carbon dioxide and urea are both metabolic waste products found in the blood. If they were allowed to build up, they would become toxic to the body's cells.

## Mark scheme (5 marks)

1. Carbon dioxide is produced during (aerobic) respiration
2. Carbon dioxide is excreted by the lungs
3. Urea is produced by the breakdown/deamination of excess amino acids
4. Urea is produced in the liver
5. Urea is excreted by the kidneys (in urine)

## Key terms

- [urea](https://www.gradenine.co.uk/glossary/urea)
- [carbon dioxide](https://www.gradenine.co.uk/glossary/carbon-dioxide)

## 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-biology-teacher-explains-to-a-cc467cad) · Published by Druglandscape Ltd.