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B5- CELL RECOGNITION AND THE IMMUNE SYSTEM > 5.7- THE HUMAN IMMUNODEFICIENCY VIRUS (HIV) > Flashcards

5.7- THE HUMAN IMMUNODEFICIENCY VIRUS (HIV) Flashcards

1
Q

What does the human immunodeficiency virus cause?

A

disease acquired immune deficiency syndrome (AIDS)

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2
Q

What is on the outside of the HIV structure?

A

lipid envelope embedded in which are peg-like attachment proteins

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3
Q

What is inside the lipid envelope of the HIV virus?

A

protein layer called capsid

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4
Q

What does the capsid of the HIV virus enclose?

A

two single strands of RNA + some enzymes

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5
Q

What is one of the enzymes that is enclosed in the capsid of the HIV virus?

A

reverse transcriptase

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6
Q

Why is reverse transcriptase so-called?

A

it catalyses the production of DNA from RNA- reverse reaction to that of transcriptase

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7
Q

What group of viruses does HIV belong to?

A

retroviruses

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8
Q

Why does HIV belong to the group retroviruses?

A

presence of reverse transcriptase + consequent ability to make DNA from RNA

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9
Q

As HIV is a virus can it replicate by itslef?

A

no

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10
Q

As HIV is a virus and cannot replicate by itself, what does it do?

A

uses its genetic material to instruct host cell’s biochemical mechanisms to produce components required to make new HIV

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11
Q

How HIV replicates: what does HIV do following infection? (1)

A

HIV enters bloodstream + circulates around body

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12
Q

How HIV replicates: what does a protein on HIV do? (2)

A

protein on HIV readily binds to protein called CD4

while this protein occurs on number of different cells, HIV most frequently attaches to T helper cells

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13
Q

How HIV replicates: what does the protein capsid do and then what happens? (3)

A

protein capsid fuses with cell-surface membrane

RNA + enzymes of HIV enter helper T cell

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14
Q

How HIV replicates: what does the HIV reverse transcriptase do? (4)

A

HIV reverse transcriptase converts virus’s RNA into DNA

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15
Q

How HIV replicates: where is the newly made DNA moved into? (5)

A

newly made DNA moved into T helper cell’s nucleus where it’s inserted into cell’s DNA

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16
Q

How HIV replicates: what does the HIV DNA in the nucleus create? (6)

A

HIV DNA in nucleus creates messenger RNA (mRNA) using cell’s enzymes

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17
Q

What does the mRNA produced by the HIV DNA in the nucleus contain?

A

instructions for making new viral proteins + RNA to go into new HIV

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18
Q

How HIV replicates: where does the mRNA from the HIV DNA pass out of and do? (7)

A

passes out of nucleus through nuclear pores + uses cell’s protein synthesis mechanisms to make HIV particles

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19
Q

How HIV replicates: what does the HIV particles break away from? (8)

A

HIV particles break away from helper T cell with piece of its cell-surface membrane surrounding them which forms their lipid envelope

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20
Q

What is a person said to be once infected with HIV?

A

HIV positive

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21
Q

What does the replication of HIV often do and then what happens?

A

often goes into dormancy + only recommences, leading to AIDS, many yrs later

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22
Q

What does the HIV virus specifically attack?

A

helper T cells

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23
Q

How does HIV cause AIDS?

A

by killing or interfering with normal functioning of helper T cells

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24
Q

Between how many helper T cells does an uninfected person normally have in each mm3 of blood?

A

normally has between 800 to 1200 helper T cells in each mm3 of blood

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25
Q

How many helper T cells can a person suffering from AIDS have in each mm3 of blood?

A

200mm-3

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26
Q

What are helper T cells important in?

A

cell-mediated immunity

27
Q

What happens without a sufficient number of helper T cells?

A

immune system cannot stimulate B cells to produce antibodies or cytotoxic T cells that kills cells infected by pathogens

28
Q

What can also be affected other than helper T cells?

A

memory cells may also become infected or destroyed

29
Q

As memory cells are infected/ destroyed, what is the body unable to do?

A

unable to produce adequate immune response + becomes susceptible to other infections + cancers

30
Q

What do many AIDS sufferers develop infections of and experience?

A

infections- lungs, intestines, brain + eyes

experience- weight loss + diarrhoea

31
Q

What ultimately causes the death of someone with AIDS?

A

secondary diseases

32
Q

Does HIV kill individual directly?

A

no

33
Q

What does HIV do by infecting the immune system?

A

prevents it from functioning normally

34
Q

As HIV prevents the immune system from functioning normally, what are those infected unable to do?

A

unable to respond effectively to other pathogens

these infections rather than HIV that ultimately cause ill health + eventual death

35
Q

What does ELISA stand for?

A

enzyme linked immunosorbant assay

36
Q

What does ELISA use?

A

antibodies to detect presence of protein + quantity

37
Q

How sensitive is ELISA?

A

extremely sensitive

38
Q

As ELISA is extremely sensitive, what can it do?

A

can detect very small amounts of a molecule

39
Q

ELISA test: first step (applying)

A

apply sample to surface, e.g. slide, to which all antigens in sample will attach

40
Q

ELISA test: second step (washing)

A

wash surface several time to remove any unattached antigens

41
Q

ELISA test: third step (adding)

A

add antibody that’s specific to antigen we’re trying to detect + leave the two to bind together

42
Q

ELISA test: fourth step (washing)

A

wash surface to remove excess antibody

43
Q

ELISA test: fifth step (adding)

A

add second antibody that binds with first antibody

second antibody has enzyme attached to it

44
Q

ELISA test: sixth step (adding)

A

add colourless substrate of enzyme

enzyme acts on substrate to change it into coloured product

45
Q

ELISA test: seventh step (amount of antigen relative to)

A

amount of antigen relative to intensity of colour that develops

46
Q

What is the basic technique of the ELISA test be used to detect?

A

HIV + pathogens of diseases including tuberculosis + hepatitis

47
Q

What is ELISA especially useful for?

A

where quantity of antigen needs to be measured

48
Q

Why is ELISA very useful in drug + allergen tests?

A

mere presence of drug often less important than its quantity as many drugs found naturally in low concentrations

49
Q

What is one way in which antibiotics work?

A

preventing bacteria from making normal cell walls

50
Q

What is constantly entering bacterial cells?

A

water by osmosis

51
Q

What would water entering by osmosis constantly normally cause?

A

would normally cause cell to burst

52
Q

Why does the bacterial cell not burst when water is entering by osmosis constantly?

A

due to wall that surrounds all bacterial cells

53
Q

What is the bacterial cell wall made of?

A

murein- tough material that’s not easily stretched

54
Q

As water enters the bacterial cell by osmosis, what happens to the cell?

A

cell expands + pushes against cell wall

55
Q

What does the cell wall of bacterial cells do when water enters by osmosis?

A

resists expansion + so halts further entry of water

56
Q

Why does the cell wall of bacterial cells resist expansion when water enters by osmosis?

A

as it’s relatively inelastic

57
Q

What do antibiotics such as penicillin inhibit?

A

inhibit certain enzymes required for synthesis + assembly of peptide cross-linkages in bacterial cell walls

58
Q

As antibiotics i.e. penicillin inhibit certain enzymes required for synthesis + assembly of peptide cross-linkages in bacterial cell walls, what does this do?

A

weakens cells walls, making them unable to withstand pressure

59
Q

As the weakened cell walls are unable to withstand the pressure from the antibiotics i.e. penicillin, what happens?

A

water enters naturally by osmosis, cell bursts + bacterium dies

60
Q

What do viruses rely on host cells for?

A

to carry out their metabolic activities

61
Q

What do viruses lack as they rely on host cells to carry out their metabolic activities?

A

lack their own metabolic pathways + cell structures

62
Q

Why are antibiotics ineffective against viruses?

A

no metabolic mechanisms or cell structures for them to disrupt

63
Q

What do viruses have instead of a murein cell wall as in bacterial cells?

A

have a protein coat

64
Q

As viruses don’t have a murein cell wall what does this mean for anitbiotics?

A

don’t have sites where antibiotics can work

B5- CELL RECOGNITION AND THE IMMUNE SYSTEM (7 decks)

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