Cholera

Cholera

1. Prokaryotic cells

   • 'Before nucleus'
     • No nucleus or nucleolus
     • Only a diffuse area of nuclear material
   • Circular strands of DNA and a plasmid but no chromosomes
   • No membrane-bound organelles
   • Smaller 70S ribosomes
   • Cell wall made of peptidoglycan

2. Bacterial cell

   • Cell wall
     • Protects against mechanical damage
     • Excludes certain substances
     • Made of peptidoglycan
   • Capsule
     • Slime layers that protects bacterium
     • Sticks cells together
   • Cell-surface membrane
     • Differentially permeable membrane
   • Flagellum
     • Rigid, corkscrew shape
     • Movement
   • Circular DNA
     • Genetic information for replication
   • Plasmid
     • Genes to aid survival (antibacterial resistance)

3. Vibrio cholerae

   • Transmitted through water ingested and contaminated with faecal matter
   • Most killed in stomach acid
   • Produces a toxin
     • Causes loss of microvilli

4. Mechanism of infection

   • 1. Bacterium enters the small intestine and flagellum propels itself into mucus
   • 2. Produces a toxin made up of two parts
   • 3. One part binds to specific glycoprotein receptors of epithelial cells
   • 4. The other toxic part enters the cells and causes chloride channel ions to open
   • 5. Chloride ions flow into lumen of the small intestine
   • 6. This raises the cells water potential and lowers the lumen's water potential
   • 7. Ions move into the epithelial cells from the surrounding tissues and blood due to conc. gradient and loss of chloride ions
   • 8. Water moves by osmosis from the cells and other tissues into the lumen

5. Symptoms

   • Diarrhoea
   • Dehydration
   • Some show no symptoms

6. Treatment

   • Oral rehydration threapy
     • Makes use of alternative carrier proteins in epithelial cells
     • Stimulates sodium ion uptake
   • Drinking water is ineffective as intestine isn't absorbing water
   • Water
     • Rehydrate cells
   • Sodium
     • Make optimum use of sodium-glucose channel proteins
   • Glucose
     • Energy and sodium ion uptake
   • Potassium
     • Stimulate appetite
   • Other electrolytes
     • Prevent imblanace

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