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Microbiology > Viruses > Flashcards

Viruses Flashcards

1
Q

what does obligate mean?

A

relies on the host cell for life

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2
Q

what does the host cell provide for the virus?

A

nucleotides, ribosomes and amino acids, ATP and Golgi and the ER

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3
Q

what do viruses use the provided nucleotides for?

A

nucleic acid production

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4
Q

what do viruses use the provided golgi and ER for?

A

protein processing

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5
Q

what are the catagories of viruses?

A

nucleic acid either RNA/DNA, capsid symmetry, presence of envelope and the genome characteristics

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6
Q

what are the different structures of capsid symmetry?

A

helical, icosahedral or complex

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7
Q

what are the main viral characteristics?

A

nucleic acid, protein coat, maybe an envelope or capsule

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8
Q

what is a nucleocapsid?

A

the capsid and the nucleic acid

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9
Q

what are capsomers?

A

the proteins that make up the capsid, they form the capsid spontaneously

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10
Q

what shapes can the capsid have?

A

polyhedral or helical

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11
Q

what is the arrangement of a nucleocapsid?

A

highly symmetrical, composed of one protein and capsid is formed via self-assembly by capsomeres

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12
Q

what is a bacteriophage?

A

viruses that infect and replicate within bacteria

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13
Q

why are bacteriophages bad for bacteria?

A

highly virulent

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14
Q

what is a bacteriophage classified by?

A

nucleic acid type and shape

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15
Q

what are the physical features of a bacteriophage?

A

head, collar, tail and tail pins, tail fibres

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16
Q

how many steps in a bacteriophage life cycle? what are they?

A

5; attachment, penetration, synthesis of nucleic acid, assembly, lysis

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17
Q

how are bacteriophages specific?

A

infect one species only

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18
Q

how do bacteriophages attach to host cells?

A

viruses have attachment proteins on their surface which attaches to specific receptors on the host cell surface

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19
Q

what are the receptors that the virus attaches too?

A

essential proteins on the surface of the host cell

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20
Q

what are two examples of bacteriophages?

A

T4 and lambda

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21
Q

what is different about the structure of lambda?

A

no tail pins or tail fibres

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22
Q

what is the difference between lambda and T4?

A

lambda is temperate yet T4 is virulent

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23
Q

what are the two life cycles of lambda?

A

lytic and lysogenic

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24
Q

what is the lytic cycle?

A

bacteria genome is destroyed and the cell becomes a factory for making bacteriophages

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25
Q

what is the lysogenic cycle?

A

DNA of the virus gets inserted into the bacterial genome so it becomes a prophage, which is passed on to future generations

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26
Q

how can a lysogenic cycle turn into a lytic cycle?

A

a prophage exits the bacterial chromosome

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27
Q

what is the only function of T4?

A

the lytic cycle

28
Q

how is phage DNA inserted into bacterial genome?

A

via genetic recombination which occurs at a specific point on the genome

29
Q

what occurs in assembly and packaging of bacteriophages?

A

stage of maturation where the viral components are assembled into virions

30
Q

what is an example of a plant virus?

A

tobacco mosaic virus

31
Q

what are the features of tobacco virus?

A

helical symmetry, 2130 identical capsomers, helical nucleocapsid

32
Q

what kind of nucleic acid does the tobacco virus have?

A

RNA

33
Q

how do plant viruses enter a cell?

A

endocytosis

34
Q

how does the tobacco virus spread across the leaf?

A

infects all cells as they are connected together

35
Q

what kind of virus is the most varied?

A

animal viruses

36
Q

what is a key structure of an animal virus?

A

they have an envelope

37
Q

what is an example of a non-enveloped virus?

A

picornavirus

38
Q

what does picornavirus look like?

A

icosahedral virus without an envelope

39
Q

where does the envelope come from?

A

either the cell, golgi or nuclear membrane

40
Q

how do enveloped viruses escape from a cell?

A

via budding or bursting

41
Q

what are some examples of enveloped viruses?

A

measles, influenza

42
Q

what are matrix proteins?

A

they connect the nucleocapsid to the membrane

43
Q

how are the surface glycoproteins useful?

A

act as main antigens for immune system

44
Q

what are the two glycoproteins of influenza?

A

H-haemaglutanin and N-neuraminidase

45
Q

what makes it difficult for the immune system to recognise influenza?

A

they can change their surface proteins visa antigenic shift

46
Q

what are the methods of entry of a virus?

A

direct penetration, membrane fusion and endocytosis

47
Q

how do naked viruses enter?

A

direct penetration

48
Q

how do enveloped viruses enter?

A

membrane fusion

49
Q

what does the ER of the cell do in an enveloped virus life cycle?

A

makes viral glycoproteins

50
Q

where in the cell is enveloped virus assembly taken place?

A

the golgi, nuclear or cell membrane

51
Q

does an enveloped virus life cycle kill the cell initially?

A

no, the cell only dies once it runs out of resources

52
Q

how do the assembled enveloped virus escape from the cell?

A

endocytosis

53
Q

what is HIV?

A

ss enveloped RNA virus

54
Q

what is a retrovirus?

A

the RNA of the virus gets converted into DNA via retrotranscriptase

55
Q

how is the HIV viral DNA incorporated into host DNA?

A

imported into the nucleus

56
Q

can HIV become latent? what does this mean?

A

yes, which means it can lie dormant within the cell

57
Q

what are the effects of viruses on cells?

A

cytopathic effects, transformation into tumour cell, lysis, persistent infection, latent infection

58
Q

what is persistent infection?

A

slow release of the virus without cell death

59
Q

what happens in latent infection of a cell?

A

virus is present but not causing harm, later emerges in lytic infection

60
Q

how do you grow viruses in culture?

A

provide with specific types of cells so you can analyse their effects

61
Q

what is primary cell culture? why is it listed?

A

cells obtained from animal tissue yet limited life of the tissue

62
Q

what is diploid cell lines? why is use limited?

A

homogenous cells from embryos, yet divide about 100 times and then they die

63
Q

what is continuous cell lines?

A

use cancerous cells to produce an immortal cell line that does not stop growing

64
Q

how do you count viruses?

A

plaque assay

65
Q

what is a plaque assay?

A

virus innoculated on a single monolayer and an overlay of agar is added, causing plaques of the dead cells to form in the monolayer

Microbiology (11 decks)

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