cholera Flashcards
Infection by the cholera bacterium can cause acute diarrhoea. Explain how.
- Toxin (produced by bacterium) causes (chloride) ions to move into (lumen of) intestine2. Water potential (of intestine contents) falls / water moves by osmosis into intestine/out of cells
In areas where there are repeated outbreaks of cholera, most people who become infected by cholera bacteria do not become ill. Suggest and explain one reason why.
- Have produced memory cells;2. After previous infection/vaccination;3. Different forms of cholera;4. Some don’t produce much/any toxins;5. Few bacteria ingested;6. Not enough toxin to produce symptoms;7. Some people naturally resistant to bacterium;8. Because of structure of cell membranes / amount of secretions eg bile/pancreatic juices;
Cholera bacteria produce toxins which increase secretion of chloride ions into the lumen of the intestine.Explain why this results in severe diarrhoea (watery faeces). How is it treated ?
- Water lost into gut/water moves into gut/ water leaves cells;2. Low(er) water potential of intestine/gut (lumen);3. Osmosis/movement down a WP gradient;4. Less/not enough water (re)absorbed;ORAL REHYDRATION SALTS (ORS)
Oral rehydration solutions (ORS) are used to treat diarrhoeal disease. What does an ORS consist of and how does it work?
- Contains glucose/starch/ carbohydrate / sugar2. Sodium/salt3. Co-transport / symport4. Sodium and glucose taken up (from lumen)5. Lowers water potential in cells/ increases water potential gradient6. Water taken up by osmosis;
Vaccines protect people against disease. Explain how.
- Vaccines contain antigens / antigens are injected2. Dead pathogens / weakened pathogens3. Memory cells made4. On second exposure memory cells produce antibodies / become active / recognise pathogens5. Rapidly produce antibodies / produces more antibodies6. Antibodies destroy pathogens7. Herd effect / fewer people to pass on disease;
Cholera bacteria are prokaryotic cells. Give three structures found in prokaryotic cells but not in eukaryotic cells.
Capsule / glycocalyx / slime layer;Circular / ring of / non-linear DNA / DNA without histones; Plasmid;Flagellum;Pilus;Small / less dense / 70s ribosomes
Cholera bacteria cause an increase in the secretion of chloride ions into the small intestine. Use your knowledge of water potential to explain how the increased secretion of chloride ions causes diarrhoea.
Lower / more negative water potential (in lumen / intestine / gut)Water enters (intestine) / leaves (body) cells by osmosis;
People with diarrhoea suffer fluid loss. They can use oral rehydration solutions (ORS) to replace the lost fluid. The mixture used to make an oral rehydration solution is stored as a powder. The powder can be made into a solution with boiled water.Why must boiled water be used to make an ORS?
Kills / destroys bacteriaORDoes not contain bacteria / removes bacteria / sterile / prevents bacteria entering body;
The mixture used to make the ORS contains glucose. Give one other substance that must be present in the mixture.
Sodium (ions) / potassium (ions) / chloride (ions) / citrate (ions);
How does cholera make humans ill?
bacteria enter via CONTAMINATED water, some survive acidity of stomach (1) bacterium PROPELS through intestinal lining with flagellum (1) secretes a PROTEIN that binds to RECEPTORS on epithelial cells (1) bacterium also secretes a toxic protein that interferes with chloride channels (1) chloride ions flood lumen, water potential is more negative in lumen (1) from cells to lumen by osmois, causes diarrhoea (1)
How does ORT replace water loss?
encourages the cells to uptake SODIUM and GLUCOSE (1); water potential in the cells becomes more negative (1); water moves from intestine to cells by osmosis (1)
How does lactose intolerance cause diarrhoea?
Undigested lactose in small intestine causes water potential to become MORE negative (1); water moves from the epithelial cells into the lumen (1); by OSMOSIS (1)
Cholera bacteria cause an increase in the secretion of chloride ions into the small intestine. Use your knowledge of water potential to explain how the increased secretion of chloride ions causes diarrhoea.
Lower / more negative water potential (in lumen / intestine / gut)Water enters (intestine) / leaves (body) cells by osmosis;
People with diarrhoea suffer fluid loss. They can use oral rehydration solutions (ORS) to replace the lost fluid. The mixture used to make an oral rehydration solution is stored as a powder. The powder can be made into a solution with boiled water.Why must boiled water be used to make an ORS?
Kills / destroys bacteriaDoes not contain bacteria / removes bacteria / sterile / prevents bacteria entering body;
The mixture used to make the ORS contains glucose. Give one other substance that must be present in the mixture.
Sodium (ions) potassium (ions) chloride (ions) citrate (ions);
