# Chlamydia is a communicable disease caused by a bacterium. Explain how the human body attempts to defend itself against a Chlamydia infection, from the point at which the bacterium first enters the body to the point at which it is destroyed.

> Eduqas A-Level Biology — 3.5 Human impact on the environment · Explain · 5 marks

## Mark scheme (5 marks)

1. Non-specific defence: skin / mucus / chemical barriers act as a first line of defence to prevent the pathogen entering the body
2. White blood cells detect the bacterium using receptors that identify antigens on the surface of the pathogen
3. Lymphocytes produce antibodies that are specific / complementary to the antigen on the Chlamydia bacterium
4. Antibodies bind to the antigens on the bacterium to neutralise / disable it, or clump bacteria together (agglutination) to make destruction easier
5. Phagocytes engulf and digest the bacterium / pathogen using enzymes (phagocytosis)

## Key terms

- [communicable disease](https://www.gradenine.co.uk/glossary/communicable-disease)

## Related

- [Revision notes for Eduqas A-Level Biology](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/chlamydia-is-a-communicable-disease-caused-958a7e2d) · Published by Druglandscape Ltd.