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AS Level Biology > 10. INFECTIOUS DISEASES > Flashcards

10. INFECTIOUS DISEASES Flashcards

1
Q

Drugs used for the treatment of tuberculosis

A

Isoniazid
Rifampcin (transcription inhibitor)
Streptomycin
–

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2
Q

The antimicrobial drug that is synthetic and made in a laboratory

A

Isoniazid

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3
Q

Ways in which antibiotics interfere with some aspect of growth or cell metabolism

A

PrESSS

  • activity of proteins in cell surface membrane
  • enzyme activity
  • synthesis of bacterial cell walls
  • synthesis of DNA
  • protein synthesis
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4
Q

Mode of action of penicillin

A

cell wall synthesis inhibitor

  • prevents the synthesis of cross-links between the peptidoglycan polymers in the cell wall of bacteria
  • by inhibiting the enzymes that build these cross-links
  • it is only active against bacteria while they are growing
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5
Q

Antibiotics that are cell-wall inhibitors and what they do

A 
PVC
Penicillin
Cephalosporin
Vancomycin
--> inhibit the enzymes that build cell wall cross-links
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6
Q

The enzyme secreted by growing bacterial cells that creates holes in the cell wall and mode of action of penicillin

A

autolysin

  • -> makes little holes in the cell wall
  • -> holes allow the wall to stretch so new peptidoglycan chains can link together
  • -> penicillin prevents the peptidoglycan chains from linking together, but autolysin keeps making new holes
  • -> cell wall becomes weaker and cannot withstand the high pressure of water in outside environment
  • -> water enters cell by osmosis and cell bursts
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7
Q

Mode of action of quinonine

A

interferes with DNA replication

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8
Q

Why do antibiotics not act on viruses

A
  • viruses don’t grow
  • viruses do not possess the structures that antibiotics affect
  • viruses don’t have cell walls or cells
  • viruses replicate by using host cell’s mechanisms for transcription and translation and antibiotics to do not bind to the proteins that host cells use
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9
Q

A drug that is not sensitive to Mycobacterium tuberculosis and why

A

Penicillin

  • Mycobacterium has a thick cell wall that is not very permeable
  • contains a gene that codes for a protein that catalyses the breakdown of penicillin
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10
Q

Reasons antibiotics are not sensitive to bacteria

A
  • contains gene that codes for a protein that catalyses the breakdown of antibiotic
  • contains proteins in membrane that inactivate antibiotic so it has no effect
  • contains proteins that pump out antibiotics if they enter the cytoplasm
  • antibiotic cannot bind to intended site of action
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11
Q

What enzyme can penicillin be broken down by

A

Beta-lactamase

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12
Q

When does antibiotic resistance arise

A

antibiotic resistance arises when an existing gene within the bacterial genome changes spontaneously to give rise to a nucleotide sequence that codes for a slightly different protein that is not affected by the antibiotic. a mutation

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13
Q

Why do bacteria gain resistance to antibiotics easily

A
  • have only one copy of each gene since they have only a single loop of double-stranded DNA
  • a mutant gene will have an immediate effect on any bacterium possessing it
  • bacteria divide by binary fission so each daughter cell is also resistant
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14
Q

Vertical transmission of bacterial resistance

A
  • bacterial chromosome and plasmid replicate
  • resistant parent cell divides into two by binary fission
  • daughter cells each receive a copy of the plasmid and are resistant
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15
Q

Horizontal transmission of bacterial resistance

A
  • happens during conjugation when a tube forms between two bacteria (can be of different species)
  • a single DNA strand of the plasmid is transferred
  • each bacterium then synthesises a complementary strand
  • both cells are now resistant
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16
Q

Consequences of multiple resistance of bacteria for health authorities

A

1 risk of, further spread / wider epidemic, (from people still infected)
2 reduces chance of succesful treatment / higher death rates
3 increased, treatment / hospitalisation times, takes longer to treat, a more complex treatment
4 increased costs of treatment / strain on health budget
5 risk of, further resistance / resistance to all antibiotics
6 fewer antibiotics left that are effective
7 need to find, new antibiotics / alternative treatment
8 (so) cost of research

17
Q

How can antibiotics be chosen carefully

A
  • by testing antibiotics against the strain of bacterium isolated from people
  • ensures the most effective antibiotic can be used in treatment
18
Q

What is an antitoxin

A
  • preparation of human antibodies
  • collected from blood donors who have recently been vaccinated with a particular vaccine
  • provides immediate protection but is only temporary
19
Q

Why are antitoxins temporary

A
  • they are not produced by the body’s own B cells
  • are therefore regarded as foreign themselves
  • removed from the circulation by phagocytes in the liver and spleen
20
Q

Ways in which HIV is transmitted

A
  • sexual intercourse
  • infected blood transfusions
  • sharing contaminated hypodermic needles
  • across placenta from mother to foetus
  • through breast milk
21
Q

Problems involved in controlling the spread of HIV

A
  • no cure or vaccine (because the virus changes it surface proteins)
  • drugs are expensive
  • people can be symptomless carriers and pass on the disease (due to HIV’s long latent stage)
  • testing people for HIV is considered an infringement of personal freedom
  • problems with educating about risks in poor countries
  • providing condoms and raising awareness is expensive
  • contact tracing can be expensive and difficult
  • blood is not screened or treated to kill HIV in poor countries
22
Q

What is the function of reverse transcriptase

A

uses the RNA as a template to produce DNA once the virus is inside a host cell

23
Q

What are the two glycoproteins on the outer envelope of HIV

A

gp 120

gp 41

24
Q

What is a retrovirus

A

A type of RNA virus that inserts a copy of its genome into the DNA of a host cell that it invades, thus changing the genome of that cell

25
Q

What is AIDS

A
  • a series of opportunistic infections associated with immunodeficiency
  • caused by the HIV infection
26
Q

People at high risk of getting HIV

A
  • male homosexuals who practice anal intercourse
  • people with multiple sex partners/ prostitutes
  • injecting drug users
  • haemophiliacs
27
Q

Most likely causes of death with AIDS

A

kaposi’s sarcoma
cancers of internal organs
degenerative diseases of the brain, such as dementias

28
Q

What diseases does a person with AIDS become more susceptible to

A
  • tuberculosis
  • malaria
  • malnutrition
29
Q

What does the HIV virus do

A

binds to CD4 receptors on t-helper lymphocytes

30
Q

What does zidovudine do

A
  • drug that is similar to the DNA nucleotide that contains the base thymine
  • binds to the viral enzyme reverse transcriptase and blocks its action
  • this stops the replication of the viral genetic material
  • and leads to an increase in the number of the body’s lymphocytes
31
Q

What are the problems involved with the treatment of HIV

A
  • virus changes its surface proteins (antigenic variation)
  • virus hides inside host cells (antigenic concealment)
  • drug resistance
32
Q

Why do female Anopheles mosquitoes feed on human blood

A

to obtain the protein they need to develop their eggs

33
Q

What is the appearance of red blood cells infected with malarial parasites

A

there is a ‘signet ring’ appearance of the parasites inside red blood cells

34
Q

Biological control measures that can be taken to prevent malarial infection

A
  • stocking ponds, irrigation, drainage ditches and other permanent bodies of water with fish that feed on mosquito larvae
  • spraying a preparation containing the bacterium Bacillus thuringiensis, which kills mosquito larvae but is not toxic to other forms of life
35
Q

How does multiple drug resistance arise

A
  • antibiotic course not completed so not all bacteria die
  • bacteria mutate and become resistant
  • problems with continued antibiotic supply
  • exposure to bacteria with different resistance so resistance genes passed by horizontal or vertical transmission
36
Q

Problems with the eradication of TB

A
  • vaccine doesn’t work well with everybody
  • there are symptomless carriers so it is difficult to identify infected people
  • contact tracing requires resources and is expensive
  • TB is transmitted from animals to humans
  • LEDCs have overcrowded living conditions where TB spreads easily
  • lack of availability of trained personnel
  • political problems
  • difficulty in administering drugs
  • difficult to diagnose
  • TB is opportunistic so infects people weakened with HIV
37
Q

Effect of HIV on tuberculosis

A
  • one of the first opportunistic infections to strike HIV infected people
  • reactivates dormant infections of Mycobacterium tuberculosis from childhood
  • if people are uninfected, make them susceptible to infection

AS Level Biology (10 decks)

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