# Explain how the human body uses non-specific defence systems to prevent pathogens from entering, and describe what happens when a pathogen successfully enters the body and is detected by white blood cells.

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

## Mark scheme (5 marks)

1. A non-specific physical/mechanical barrier is named and its function stated (e.g. skin acts as a physical barrier to prevent pathogen entry; hairs in the nose trap pathogens; blood clotting seals wounds)
2. A chemical barrier is named and its function stated (e.g. stomach acid / mucus / tears kill or trap pathogens)
3. White blood cells detect pathogens using receptors to identify antigens on the pathogen's surface
4. Phagocytes engulf (ingest) and digest the pathogen using enzymes (phagocytosis)
5. Lymphocytes produce antibodies that are specific/complementary to the pathogen's antigens and neutralise / disable the pathogen

## Key terms

- [non-specific defence system](https://www.gradenine.co.uk/glossary/non-specific-defence-system)

## 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/explain-how-the-human-body-uses-d496c646) · Published by Druglandscape Ltd.