# Explain why cigarette smoking increases the risk of lung infections and reduces the efficiency of gas exchange in the lungs.

> WJEC GCSE Biology (Wales) — 1.2.2 The respiratory system · Explain · 4 marks

## Mark scheme (4 marks)

1. Smoking damages or destroys cilia (on the lining of the airways/trachea/bronchi)
2. Without functioning cilia, mucus and trapped pathogens/bacteria/viruses are not swept away from the lungs, increasing risk of infection
3. Smoking causes the walls between alveoli to break down, reducing the surface area available for gas exchange
4. Reduced surface area means less oxygen can diffuse into the blood (and less carbon dioxide can diffuse out), so gas exchange is less efficient

## Key terms

- [gas exchange](https://www.gradenine.co.uk/glossary/gas-exchange)

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](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/explain-why-cigarette-smoking-increases-the-6d9a6c01) · Published by Druglandscape Ltd.