What is the cause of cholera?
Bacterium - Vibrio cholerae
Describe the physical appearance of Vibrio cholerae
- Curved, rod-shaped bacterium
- Has a flagellum
Name 4 ways cholera is transmitted
- Drinking water that hasn't been purified
- Untreated sewage leaching into water courses
- Contaminated food
- Eating other organisms (e.g. shell fish) that have fed on untreated sewage
Name 3 precautions to prevent the transmission of cholera
- Effective water / sewage treatment
- Improved hygiene
- Prevent water contamination
- Quarantining of affected area
Name two symptoms of cholera
Describe how cholera bacterium causes disease (6 steps)
- In small intestine: bacteria uses its flagella to go through mucus lining of intestine
Produce toxin protein which binds to specific receptors on cell membrane
- Toxic protein causes ion channels to open & chloride ions move into lumen
- Loss of ions from epithelial cells = concentration gradient → ions diffuse into epithelial cells from surrounding tissues & blood
- ↓Ψw in lumen = water move by osmosis from blood/tissues into lumen down Ψw gradient
- Less water reabsorbed = symptoms of cholera
Why does the cholera toxin (exotoxin) only affects the small intestine?
- Exotoxin specific to epithelial cells in small intestine
- Only binds to these specific receptors on membrane
- ∵ they're complementary shape of exotoxin
Name 3 causes of diarrhoea
- Damage to epithelial cells lining intestine
- Loss of microvilli due to toxins
- Excessive secretion of water due to toxins
What is just drinking water ineffective to cure cholera?
- Water is not being absorbed from intestine
- Doesn't replace electrolytes (ions) that are being lost from epithelial cells of intestine
Name 5 things a rehydration solution contains
- Other electrolytes
Why does a rehydration solution contain sodium?
To replace sodium ions lost from epithelium of intestine
Why does a rehydration solution contain water?
To rehydrate tissues
Why does a rehydration solution contain potassium?
Replace lost potassium ions and stimulate appetite
Why does a rehydration solution contain glucose?
To stimulate uptake of sodium ions i.e. make use of the sodium-glucose carrier proteins
& provide energy
Why does a rehydration solution contain electrolytes?
Help prevent electrolyte imbalance
How should the rehydration solution be taken?
Regularly and in large amounts, throughout illness
Explain how an oral rehydration solution replaces water lost by diarrhoea (4)