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Biology Foundation > XABY02 MICROBIAL DISEASES > Flashcards

XABY02 MICROBIAL DISEASES Flashcards

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1
Q

What is pathogenicity?

A

The ability of bacteria to cause harm

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2
Q

What are the two ways a bacterium can cause harm?

A
  1. Damaging host tissues by entering and reproducing inside cells
  2. Producing toxins
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3
Q

What are the four factors affecting pathogenicity?

A
  1. features of cell wall and capsule (affecting attachment and entry to host cell)
  2. types of toxins (endotoxins and exotoxins)
  3. infectivity of bacteria
  4. invasiveness of bacteria
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4
Q

What allows a bacterium to attach to protein receptors of host cell membrane?

A

The specific complementary structures of Ligands (polysaccharides) and Glycocalyx (glycoproteins) of bacterial cell wall

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5
Q

Aside from cell membrane binding, what are two other ways entry of bacteria can also occur?

A
  1. production of enzymes by pathogen, damages host cell membrane
  2. endocytosis, bacteria engulfed by host e.g. white blood
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6
Q

What is a toxin?

A

A molecule with harmful effects on the body

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7
Q

What are exotoxins?

A

Protein secreted or leaked from bacteria

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8
Q

What are endotoxins?

A

Lipopolysaccharides present in bacterial cell walls, usually released when bacterial cell wall breaks up after death

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9
Q

What determines infectivity?

A

The number of bacteria needed to cause infection

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10
Q

What is an example of a highly infective disease?

A

Typhoid Fever

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11
Q

What is an example of a disease that is not highly infective?

A

Food poisoning (caused by Salmonella)

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12
Q

What two diseases are caused by different species of Salmonella bacteria?

A

Typhoid Fever and food poisoning

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13
Q

What is invasiveness?

A

The ability of bacteria to spread from where it entered, to other tissues and to multiply here

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14
Q

Which systems play a part in the invasiveness of bacteria?

A

Lymph and blood (circulatory) systems

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15
Q

What two things must bacteria be able to do in order to be invasive?

A
  1. Avoid phagocytosis and all other body defences

2. To be able to get through tough fibres, connective tissues and intercellular cement

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16
Q

What two diseases are caused by particularly invasive bacteria?

A
  1. Bubonic Plague

2. Anthrax

17
Q

What can invasive bacteria do in regards to toxins?

A

Produce toxins that spread through body and damage tissues far away from initial source of infection

18
Q

What are the 6 methods of transmission of disease?

A
  1. airborne/droplet infection
  2. food-borne
  3. water-borne
  4. contact (skin to skin, clothing to skin)
  5. sexual intercourse
  6. vector-borne
19
Q

How is Cholera transmitted?

A

Ingestion of water and rarely food contaminated by faecal material containing the pathogen

20
Q

What kind of disease is Cholera?

A

water-borne

21
Q

What bacteria is Cholera caused by?

A

Vibrio Cholerae

22
Q

Give 3 ways that Cholera arise in communities

A
  1. drinking water not properly purified
  2. untreated sewage leaks into water courses
  3. food contaminated by those preparing/serving it
23
Q

Does Vibrio Cholerae posses a flagellum?

A

Yes

24
Q

How is diarrhoea treated?

A

By restoring water and ions lost by Oral Rehydration Solution

25
Q

What 4 things does an Oral Rehydration Solution contain?

A

Water, sodium ions, chloride ions and glucose

26
Q

Why is ORS successful in treatment of diarrhoea?

A

It uses the co-transport protein, which bacterial infections tend not to have an effect on

27
Q

What are the 5 symptoms of Cholera?

A
  1. diarrhoea
  2. dehydration
  3. stomach cramps
  4. vomiting
  5. fever
28
Q

What are the 4 steps of the process of the Oral Rehydration Solution?

A
  1. sodium ions and glucose in ORS taken up by co-transport protein in epithelial cells
  2. water potential of epithelial cell reduced and lower than water potential of lumen
  3. water in ORS solution then moves from lumen to cell by osmosis
  4. water moves into blood and patient rehydrated
29
Q

How does Vibrio Cholerae

cause harm?

A

Bacteria produce a toxin that acts on epithelial cells of small intestine which causes changes in membrane permeability

30
Q

What is the process in which the Vibrio Cholerae toxin causes symptoms of Cholera? (7 STEPS)

A
  1. toxin binds to protein receptor in cell membrane of epithelial cells of small intestine
  2. shape of toxin complementary to binding site on receptor
  3. attachment of toxin to receptor causes ion channels to open
  4. chloride ions diffuse into lumen of intestine
  5. lowers the water potential of the lumen, and raises the water potential of epithelial cells
  6. water flows along water potential gradient from cells and blood into lumen by osmosis
  7. which causes diarrhoea
31
Q

Why were trialled Oral Rehydration Solutions with more glucose tested and rejected?

A
  • Additional glucose lowered water potential in lumen of small intestine
  • So much it started to draw even more water from epithelial cells
  • made dehydration even worse
32
Q

In developing and testing ORS, what was used instead of glucose and why? (3 reasons)

A

Starch
Because:
1. it is insoluble and has no osmotic effect
2. it is slowly hydrolysed by amylase and maltase to glucose monomers
3. because glucose is released slowly from starch, it can be taken up at same rate by co-transport

Biology Foundation (5 decks)

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