# Describe how the human body defends itself against pathogens before they enter the body, and explain what happens when a pathogen does manage to enter the bloodstream.

> Eduqas A-Level Biology — 3.1 Photosynthesis · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. Named non-specific physical/mechanical barrier (e.g. skin, hairs in nose, blood clotting)
2. Named non-specific chemical barrier (e.g. mucus, stomach acid, tears)
3. Phagocytes engulf / ingest and digest pathogens (phagocytosis)
4. Lymphocytes produce antibodies that bind to antigens on the pathogen to neutralise it
5. Memory cells remain after infection so that if the same pathogen enters again, a faster immune response occurs

## Related

- [Revision notes for Eduqas A-Level Biology](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/describe-how-the-human-body-defends-1ae4778b) · Published by Druglandscape Ltd.