AS Biology - AQA

  • Created by: ayesha
  • Created on: 08-01-12 18:34


Explain how ORS replaces water lost by diarrhoea.

ORS increase the uptake of sodium ions, glucose, sugars and salts into the cells, via co-transport proteins. This means the water potential in the cell lowers and therefore water moves in via osmosis.

(Toxins produced by cholera bacteria affects the transport of ions from the epithelial cells lining but has very little effect on the co-transport proteims that re-absorb ions)

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Cholera bacterium are prokaryotes and don't have a nucleus. It does contain DNA but only in a small loop in the cytoplasm of the cell.

Prokaryote means 'before the nucleus'

A cholera bacterium is surrounded by a cell surface membrane. Outside the membrane is a cell wall. Outside the cell wall is another layer called the protective capsule. A cholera bacterium has a flagellum which help the cell to move.

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