CholeraSpec 10.1.16, 10.1.17
Cholera is a disease caused by a bacterium. It is transmitted in contaminated water, so it spreads where drinking water is not clean or sewage is not treated.
The cholera bacterium lives in the small intestine and produces a toxin. The toxin has these effects:
- The toxin causes cells lining the small intestine to secrete chloride ions into the small intestine.
- The chloride ions lower the water potential in the gut, so water moves into the gut from the blood by osmosis.
- The extra water causes diarrhoea.
- Large amounts of water and ions are lost from the body, so the person becomes dehydrated and loses ions from the blood.
(opens full size in a new tab)Exam tip:
Put the sequence in order: toxin, chloride ions secreted, water moves in by osmosis, diarrhoea. Name osmosis.
Quick check
What is a pathogen?
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A disease-causing organism.
What is a transmissible disease?
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A disease in which the pathogen can be passed from one host to another.
Name the body defences in the syllabus.
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Skin, hairs in the nose, mucus, stomach acid and white blood cells.
Supplement Which route of transmission is cholera associated with?
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Contaminated water.