Flashcards in 3.10 Cholera Deck (35):
What is the agent which causes cholera?
A curved rod-shaped bacterium with flagellum at one end called vibrio cholerae
Are bacteria, prokaryotic cells or eukaryotic cells?
Describe the nucleus of prokaryotic cells/eukaryotic cells
Prokaryotic cells: no true nucleus, only a diffuse area of nuclear material with no nuclear envelope
Eukaryotic cells: distinct nucleus with a nuclear envelope
Describe the nucleolus of prokaryotic cells/eukaryotic cells
Prokaryotic cells: no nucleolus
Eukaryotic cells: nucleolus is present
Describe the genetic material of prokaryotic cells/eukaryotic cells
Prokaryotic cells: circular strands of DNA but no chromosomes
Eukaryotic cells: chromosomes present, in which DNA is located
Are prokaryotic or eukaryotic cells membrane-bounded?
Prokaryotic cells: no membrane-bounded organelles
Eukaryotic cells: membrane-bounded organelles such as mitochondria present
Are there chloroplasts in prokaryotic/eukaryotic cells?
Prokaryotic cells: no chloroplasts, only photosynthetic regions in some bacteria
Eukaryotic cells: chloroplasts present in plants and algae
Describe the ribosomes in prokaryotic and eukaryotic cells...
Prokaryotic cells: ribosomes are smaller 70s
Eukaryotic cells: ribosomes are larger 80s
Describe the endoplasmic reticulum in prokaryotic and eukaryotic cells...
Prokaryotic cells: no endoplasmic reticulum or associated Golgi apparatus and lysosomes
Eukaryotic cells: endoplasmic reticulum present along with Golgi apparatus and lysosomes
Describe the cell wall in prokaryotic/eukaryotic cells
Prokaryotic: cell wall made of peptigodlycan (polymer of polysaccharides and proteins)
Eukaryotic: where present cell wall is made mostly of cellulose (or chitin or fungi)
What property of bacteria is a cause of their success?
Their small size - ranging from 0.1-10 micrometers in length
List the structures found in a bacterial cell.(CCCCFP)
Describe the role of a bacterial cell wall
A physical barrier that protects against mechanical damage and excludes certain substances
Describe the role of a bacterial capsule
Protects bacterium from other cells and helps groups of bacteria to stick together for further protection.
Describe the role of a bacterial cell-surface membrane
Acts as a differentially permeable layer which controls the entry and exit of chemicals
Describe the role of bacterial flagellum
Aids movement of bacterium because it's rigid corkscrew shape and rotating base help the cell spin through fluids.
Describe the role of a bacterial circular DNA
Possesses the genetic information for the replication of bacterial cells
Describe the role of a bacterial plasmid
Possesses genes that aid the survival of bacteria in adverse conditions, e.g produces enzymes which break down antibiotics
In genetic engineering plasmids are used as...
Vectors (carriers of genetic information)
The bacterial capsule is also referred to as...
A mucilaginous layer of slime
What are the main symptoms of cholera?
Diarrhoea and consequently dehydration.
Some people infected with the cholera bacterium show...
Few if any symptoms and act as carriers
How is Vibrio cholerae transmitted?
By the ingestion of water or more rarely food that has been contaminated with faecal material containing this pathogen.
How are the symptoms of cholera caused? (Food to getting into intestine)
-most Vibrio cholerae ingested are killed by the acidic conditions of the stomach - but few survive (especially if the pH is above 4.5)
- on reaching the small intestine the bacteria use their flagella, through the mucus lining of the intestinal wall
How are the symptoms of cholera caused? (From getting into the intestinal wall to opening the ion channels)
- the bacterium start to produce a toxin protein. It has 2 parts:
- one part binds to the specific carbohydrate receptors on the cell surface membrane (AS ONLY THE EPITHELIAL CELLS OF THE SMALL INTESTINE HAVE THESE SPECIFIC RECEPTORS - the cholera toxin only effects this part of the body)
- the other part enters the epithelial cells which causes the ion channels of the cell surface membrane to open so that chloride ions (Which are normally contained in the epithelial cells flood into the intestine lumen)
How are the symptoms of cholera caused? (From opening the ion channels to diarrhoea)
- the loss of chloride ions from the epithelial cells raises their water potential, while the increase of chloride ions in the lumen of the intestine lowers it's water potential, so water flows from the cells into the lumen.
- the loss of ions from the epithelial cells establishes a concentration gradient. Ions therefore move by diffusion into the epithelial cells from the surrounding tissues including the blood. Therefore water moves from the blood and tissues into the intestine.
- this causes dehydration and diarrhoea
Food contamination by faecal material arises because:
- drinking water is not properly purified
- untreated sewage leaks into water courses
- food is contaminated by people who prepare and serve it
- organisms, especially shellfish, have fed on untreated sewage released into rivers or the sea.
What is diarrhoea?
An intestinal disorder in which watery faeces are produced frequently
What are the causes of diarrhoea?
-Damage to the epithelial cells lining the intestine
-Loss of microvilli due to toxins
-Excessive secretion of water due to toxins e.g cholera toxin
Why is drinking water an ineffective way to treat diarrhoeal diseases?
Water is not being absorbed from the intestine - water is being lost by the cells
The drinking of water does not replace the electrolytes (ions) that are being lost from the epithelial cells of the intestine
To rehydrate someone use (two options)
Oral rehydration therapy
What is the trick to developing a rehydration solution?
Use alternative sodium ion carrier proteins so that sodium ions are absorbed, so the water potential of the cells falls and water enters the cells by osmosis.
What do rehydration solutions contain?
Water - to rehydrate tissues
Sodium - to replace the sodium ions lost from the epithelium of the intestine and to make optimum use of the alternative sodium-glucose carrier proteins.
Glucose- to stimulate the uptake of sodium ions from the intestine and to provide energy
Potassium - to replace lost potassium ions and to stimulate appetite
Other electrolytes- such as chloride and citrate ions to help prevent electrolyte imbalance
Results of drug trials are published in a scientific journal before they can get a licence. Why?
To be worthy of publication any such research must conform to accepted scientific standards
Other scientists can put it though peer review
Experiments can be replicated to see if they are repeatable