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Veterinary Microbiology > Viral Structure and Multiplication > Flashcards

Viral Structure and Multiplication Flashcards

1
Q

are viruses cellular or acellular?

A

acellular

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2
Q

describe extracellular viral activity

A

inactive

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3
Q

describe intracellular viral activity

A

activate by hijacking host

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4
Q

how do viruses exist intracellularly and what do they do?

A

exists as nucleic acid, comandeer host cell

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5
Q

describe 4 overview things that viruses are

A
  1. major cause of disease
  2. important members of aquatic world
  3. importantin evolution
  4. important model systems in molecular biology
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6
Q

are viruses all bad?

A

no, they aare also important as sources of therapy

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7
Q

how are virsus used as a source of therapy?

A

use viral mechanisms with desired added genetic material

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8
Q

how are viruses important members of the aquatic world?

A

they move organic matter from particulate to dissolved

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9
Q

how are viruses important in evolution?

A

they transfer genes between bacteria, others

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10
Q

what are bacterial viruses called? (2)

A
  1. bacteriophages

2. phages

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11
Q

are there a lot of archaeal viruses?

A

no

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12
Q

what cells do most viruses infect?

A

eukaryotic

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13
Q

what 5 things are viruses classified into families based on?

A
  1. genome structure
  2. life cycle
  3. morphology
  4. genetic relatedness
  5. enveloped or non-enveloped
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14
Q

give a bacterial comparison point for the size of most viruses

A

most are 1/100th the size of E.coli

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15
Q

can viruses be seen with regular microscopes?

A

no, need an electron microscope

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16
Q

what are some of the largest animal viruses?

A

pox viruses

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17
Q

approx howsmall are most viruses?

A

20nm in diameter

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18
Q

what do all viruses contain?

A

a nucleocapsid which is composed of: nucleic acid (DNA or RNA) and a protein coat

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19
Q

what are capsids?

A

large macromolecular structures which serve as protein coat of virus

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20
Q

what is the role of capsids?

A

protect viral genetic material and aid in its transfer between host cells

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21
Q

what are capsids made of?

A

protein subunits called protomers

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22
Q

what are the 3 capsid shapes?

A
  1. helical
  2. icosahedral
  3. complex
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23
Q

describe the shape of helical capsids

A

shaped like hollow tubes with protein walls

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24
Q

what determines the length of a helical capsid?

A

amount of nucleic acid

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25
Q

how to protomers assemble in a helical capsid?

A

self-assemble

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26
Q

describe the shape of an icosahedral capsid

A

regular polyhedron with 20 equilateral faces and 12 vertices (soccer ball with faces)

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27
Q

what are capsomers in icosahedral capsids?

A

ring or knob-shaped units made of 5 (pentons) or 6 (hexons) subunit capsomers

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28
Q

give 2 examples of complex viruses

A
  1. pox virus

2. large bacteriophages with binal symmetry

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29
Q

describe the binal symmetry of large bacteriophages (complex viruses)

A

head resembles icosahedral, tail is helical

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30
Q

what is a viral envelope?

A

an outer, flexible membranous layer that binds together many viruses

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31
Q

what are animal virus envelopes made of and what do they normall arise from?

A

lipids and carbohydrates, from host cell plasma or nuclear membranes, acquired as virus leaves host

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32
Q

what do some viral envelopes contain, and what are they often used for?

A

enzymes, often used for replication of the genome

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33
Q

describe viral envelope proteins?

A

evelope proteins, which are viral encoded, may project from the envelope sirface as spikes or peplomers

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34
Q

list the 4 functions of viral envelope proteins

A
  1. involved in viral attachment to host cell
  2. used for indentification of virus
  3. may have enzymatic or other activity (ex. neuramimidase of influenza virus)
  4. may play a role in nucleic acid replication
35
Q

list and describe the 4 variations of genetic material a virus can have

A
  1. ssRNA: single-stranded RNA
  2. dsRNA: double-stranded RNA
  3. ssDNA: single stranded DNA
  4. dsDNA: double stranded DNA
36
Q

is the length of nucleic acid in all viruses the same?

A

no, it varies from virus to virus

37
Q

what are the two types of genomes a virus can have?

A
  1. linear

2. circular

38
Q

is virus genome always in one piece?

A

no, viruses can also have segmented genomes

39
Q

what does the mechanism of viral multiplication depend on? (2)

A
  1. viral structure

2. genome

40
Q

what are the 5 common steps of viral multiplication?

A
  1. attachment to host cell
  2. entry and uncoating of genome
  3. synthess
  4. assembly
  5. release into environment
41
Q

what does step 1 of viral multiplication (attachment or adsorption) depend on?

A

specific receptor attachment

42
Q

list the 3 mechanisms that the receptor determines host preference in the attachment step (step 1) of viral multiplication

A
  1. may be specific tissue (tropism)
  2. may be more than one host
  3. may be more than one receptor
43
Q

describe step 2 (entry into host) of viral multiplication (2)

A
  1. entire genome or nucleocapsid enters

2. varies between naked or enveloped virus

44
Q

what are the 3 methods of entry into the host used by viruses in viral multiplication?

A
  1. fusion of the viral envelope with host membrane; nucleocapsid enters
  2. endocytosis in vesicle; endosome aids in viral uncoating
  3. injection of nucleic acid
45
Q

what two entry mechanisms do enveloped viruses use in multiplication?

A
  1. fusion

2. endocytosis

46
Q

what entry mechanism do non-enveloped (NAKED) viruses use in multiplication?

A

injection of nucleic acid

47
Q

describe the synthesis stage of viral multiplication

A

stage where all viral components are produced

48
Q

what dictates the events that occur in the synthesis stage of viral multiplication?

A

the genome

49
Q

what are the two options the genome can choose from in the synthesis stage of viral multiplication?

A
  1. dsDNA typical flow: intructions, replication, blah blah blah
  2. RNA viral flow
50
Q

what do RNA viruses need to do for the synthesis stage of replication?

A

they must carry in or synthesize the proteins necessary to complete synthesis

51
Q

in the synthesis stage of viral replication, list and describe the 3 types of genes

A
  1. early genes: coding for synthesis proteins
  2. middle genes: coding for protein parts of virus
  3. late genes: involved in assembly
52
Q

describe the assembly stage (step 4) of viral replication

A

putting all components together to make complete virions

53
Q

is the assembly stage of viral replication simple or complex?

A

very comples

54
Q

give an example of the assembly stage of viral replication

A

the baseplate, tail fibers, and head components of bacteriophage T4 (the spooky one) are assembled separately

55
Q

what are the two types of virion release (step 5 of replication)?

A
  1. non-enveloped virus lyse the host cell

2. enveloped viruses use budding

56
Q

how do non-enveloped viruses lyse the host cell upon virion release?

A

they may attack peptidoglycan or membrane

57
Q

what happens to the host cell as a non-enveloped virus leaves?

A

it is destroyed

58
Q

describe the 4 steps of the budding process used by enveloped viruses in step 5 of replication

A
  1. viral proteins are incorporated into host membrane
  2. nucloecapsids may bind to viral proteins
  3. enveloped derived from host plasma membrane, but may take Golgi, ER, or other structures too
  4. virus may use host actin tails to propel through host membrane
59
Q

what are the 2 types of phages in bacterial and archaeal infections in terms of reproductive choices?

A
  1. temperate phage

2. virulent phage

60
Q

how many reproductive choices do virulent phages have?

61
Q

what reproductive choice do virulent phages follow?

A

multiply immediately upon entry, lyse bacterial host cell

62
Q

how many reproductive choices do temperate phages have? what are they?

A

two

  1. reproduce lytically as virulent phages do
  2. remain within host cell without destroying it
63
Q

what do many temperate phages do with their genome?

A

integrate their genome into host genome, becoming a prophage in a lysogenic bacterium, in a relationship called lysogeny

64
Q

what is the lytic cycle?

A

makes active phages

65
Q

what is the lysogenic cycle?

A

when host multiplies, phage multiplies with it, integrates genome into host, dormant phage

66
Q

what would be the advantage of a virus having a lytic cycle?

A

conditions are good now! make more active guys fast! don’t have to worry about host death before replicating

67
Q

what would be the advantage of a virus having a lysogenic cycle?

A

conditions aren’t where the virus wants, so they wait, or virus has infected all surrounding hosts due to lytic cycle, so enters lysogenic instead

68
Q

in viral infection in eukaaryotic cells, what does cytocidal infection result in?

A

cell death through lysis

69
Q

in eukaryotes, how long can persistent infections last?

70
Q

what are CPEs?

A

cytopathic effects, structural effects of viruses

71
Q

give 2 cytopathic effects of viruses on eukaryotic cells

A
  1. degenerative changes

2. abnormalities

72
Q

what can viral infection of a eukaryotic cell do to that cell?

A

transform it into a malignant cell

73
Q

what are the 4 fuck-em-up options available to viruses after penetration of a eukaryotic cell?

A
  1. transformation into a malignant cell
  2. chronic infection
  3. latent infection
  4. rapid multiplication
74
Q

what gets a virus from latent infection to rapid multiplication after penetration of a eukarytoic cell?

A

activation

75
Q

what can happen after rapid multiplication after a virus penetrates a eukaryotic cell?

A

acute infection

76
Q

what are prions?

A

proteinacous infectious particles, made ONLY of protein

77
Q

what do prions do?

A

cause a variety of neurodegenerative diseases in humans and animals

78
Q

list 3 diseases caused by prions

A
  1. scrapie in sheep
  2. bovine spongiform encephalopathy (BSE) or Mad Cow Disease
  3. Kuru and Cretzfeldt-jakob disease
79
Q

what is the broad category of diseases caused by prions called?

A

TSE (transmissible spongiform encephalopathies)

80
Q

what is the current pathogenesis of diseases caused by prions?

A

normal prion proteins exist around neural cells, and when exposed to abnormal proteins they convert normal proteins to abnormal proteins, which alters or blocks a lot of neural function

81
Q

what symptoms are caused by most prions?

A

brain lesions, behavioral changes, loss of motor functions

82
Q

is there a cure for diseases caused by prions?

A

no cure because the mechanism is not yet fully understood

83
Q

list and describe 2 additional subviral agents

A
  1. viroids: infectious agents comprised of only RNA, target plants
  2. satellites: infectious agents composed of nucleic acids and a protein coat, need a co-infector (virus) to replicate, can infect plants and animals

Veterinary Microbiology (11 decks)

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