Cholera - AQA Biology New Specification

Cholera

Cholera is a disease spread by the bacterium Vibrio Cholerae. It is spread by being ingested with food or, more commonly, water contaminated by ***** matter which itself contains the bacterium. It is for this reason that people poorer countries have a higher incidence of contracting the disease - poorer living conditions, hygiene and lack of clean water all contribute to the risks.

The bacteria itself is a prokaryotic cell (three guesses why?) and has a flagellum at one end.

How does it cause the disease?

• First, the bacteria is ingested through contaminated food or water
• When it reaches the stomach, the harsh pH destroys most of the pathogen
• However, some may survive and reach the small intestine
• Once the bacteria reach the small intestine, they use their flagellum to propel themselves into the epithelial cells lining the intestine
• After they are incide the epithelial cells, the bacteria produce exotoxins
• One part of the toxin attaches itself to the carbohydrate receptors in the epithelial cell's membrane. This receptor is found only in the small intestine and thus explains why cholera only affects this part of the body
• The toxic part of the toxin binds to ion channels on the epithelial cell
• This causes the channels to open and chloride ions flood into the lumen of the small intestine
• …