# Malaria is a communicable disease caused by a protist spread by mosquitoes. Describe how the human body's immune system responds after the Plasmodium pathogen enters the bloodstream for the first time, and explain why a second infection with the same pathogen would be dealt with more quickly.

> WJEC A-Level Biology (Wales) — 3.5 Human impact on the environment · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. White blood cells detect the Plasmodium pathogen using receptors that identify antigens on its surface
2. Lymphocytes release antibodies that are complementary / specific to the Plasmodium antigen, which bind to the antigen and neutralise the pathogen
3. Phagocytes engulf / ingest and digest the pathogen using enzymes (phagocytosis)
4. After the first infection, memory cells remain in the body
5. On second infection, memory cells rapidly divide and produce the correct antibodies more quickly, so the pathogen is destroyed before it causes disease

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/malaria-is-a-communicable-disease-caused-f8b27c86) · Published by Druglandscape Ltd.