A level Biology B · Edexcel 9BI0 · Topic 6C
Pathogens and disease
Key points
- A pathogen is a microorganism that causes disease; it may damage host tissue directly or release toxins.
- Exotoxins are proteins secreted by living bacteria; endotoxins are lipopolysaccharides in the outer membrane of Gram-negative bacteria released when they die.
- Tuberculosis is caused by Mycobacterium tuberculosis, spread by droplets; bacteria can survive inside macrophages and form tubercles in the lungs.
- HIV is a retrovirus that infects and destroys T helper cells, weakening the immune system and leading to AIDS and opportunistic infections.
- Malaria is caused by the protoctist Plasmodium, spread by the Anopheles mosquito (a vector).
- Ways of spread include droplets, contact, body fluids, contaminated food and water, and vectors.
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A pathogen is a microorganism that causes disease. The specification asks you to know a set of named pathogens, how each one is transmitted and enters its host, and how it causes harm.
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