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BIO 286 - Microbiology > Ch 8: Virus Structure and Function (Bio 286 - Microbiology) > Flashcards

Ch 8: Virus Structure and Function (Bio 286 - Microbiology) Flashcards

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Biology 101 flashcards
1
Q

lytic or virulent virus

A

virus that kills its host

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2
Q

virus

A

NOT A LIVING CELL (infects living host to replicate); depends on host metabolism (energy, materials, and enzymes); always has a small GENOME (DNA or RNA, single or double stranded); always has a PROTEIN COAT (CAPSID) that protects the genome; infect all forms of living cells; viral genomes contain information for taking over host cell and for making viral proteins (capsid, genome replication process); may carry “captured’ host genes (toxins, genomes, etc)

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3
Q

viruses always have

A

genome and capsid

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4
Q

scale of viruses

A

range from about 20-200 nm (0.02 - 0.2 micrometers)

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5
Q

viruses do not have

A

ribosomes

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6
Q

capsids

A

protein shell of viruses; ICOSAHEDRAL, FILAMENTOUS (helical), or COMPLEX, or irregular

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7
Q

icosahedral capsids

A

each triangle made up at least 3 identical capsid proteins; allows small protein to cover a large volume; structure for many animal viruses

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8
Q

filamentous (helical) capsids

A

long tube of protein with genome inside; tube made up of hundred of identical protein subunits where the tube length reflects size of viral genome

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9
Q

complex capsids

A

mixture of icosahedral and filamentous shapes; structure for many bacteriophages

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10
Q

asymmetrical (irregular) capsids

A

irregular shapes arranged without symmetry; tend to be larger viruses such as poxviruses

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11
Q

viral envelope

A

allows fusion to host cell and organelle membrane; lipid composition is stolen from host; embedded proteins may be encoded by virus; coats viral capsid as the virus leaves the cell or organelle

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12
Q

naked virus

A

virus without an envelope, typically bacteriophages

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13
Q

enveloped virus

A

lipid bilayer membranes with virus-specific proteins surround the virus

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14
Q

viral genome

A

variation in genetic material: can be either DNA or RNA, either single or double stranded, either linear or circular; includes genes encoding viral proteins (capsid, envelope proteins if virus is enveloped, any polymerase not found in host cell)

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15
Q

cells always store genetic material

A

using DNA

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16
Q

Group I virus

A

dsDNA

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17
Q

Group I virus: dsDNA

A

poxvirus

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18
Q

Group II virus

A

ssDNA

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19
Q

Group II virus: ssDNA

A

parvovirus

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20
Q

Group III virus

A

dsRNA

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21
Q

Group III virus: dsRNA

A

epizootic hemorrhagic disease

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22
Q

Group IV virus

A

(+)ssRNA

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23
Q

Group IV virus: (+)ssRNA

A

poliovirus, Covid-19

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24
Q

Group V virus

A

(-)ssRNA

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25
Q

Group V virus: (-)ssRNA

A

influenza virus

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26
Q

Group VI virus

A

RNA retrovirus

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27
Q

Group VI virus: RNA retrovirus

A

HIV [(+)ssRNA]

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28
Q

Group VII virus

A

DNA pararetrovirus

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29
Q

Group VII virus: DNA pararetrovirus

A

hepatitis B [dsDNA]

30
Q

(+) RNA

A

can be directly used to make viral proteins

31
Q

(-) RNA

A

needs to be translated to have a complementary (+) RNA made in order to make viral proteins

32
Q

reverse transcriptase (of retroviruses)

A

uses viral RNA as a template for DNA synthesis

33
Q

reverse transcriptase

A

RNA dependent DNA polymerase

34
Q

retrovirus

A

An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.

35
Q

pararetrovirus

A

Also called DNA reverse-transcribing virus. A virus with a double-stranded DNA genome that generates an RNA intermediate and thus requires reverse transcriptase to generate progeny DNA genomes.

36
Q

retrovirus virion

A

contains reverse transcriptase (which is NOT found in bacteriophage)

37
Q

viral replication occurs

A

intracellularly

38
Q

viral life cycles

A
  1. attach to host cell… 2. get viral genome into host cell… 3. replicate genome… 4. make viral proteins… 5. assemble capsids… 6. release progeny viruses from host cell
39
Q

prophage replicates along with its host

A

while lytic genes are not expressed

40
Q

permissive host

A

cell allowing complete replication cycle of a virus to occur

41
Q

bacteriophage life cycles

A
  1. ATTACH to host cell receptor proteins… 2. INJECT genome through cell wall to cytoplasm… 3. REPLICATE genome (lytic or lysogenic)… 4. SYNTHESIZE capsid proteins… 5. ASSEMBLE progeny phase… 6. LYSE cell wall to release progeny phage
42
Q

(bacteriophage) attachment to host cell proteins

A

bacterial cell receptors normally used for bacterial purposes (ex: sugar uptake, iron uptake, conjugation), so viruses will take advantage of host proteins

43
Q

(bacteriophage) injects genome through cell wall to cytoplasm

A

capsid part stays outside of host cell while only the genome is forcefully injected into the host cell

44
Q

Hershey-Chase experiment

A

(supporting injection) proves that viral DNA (not protein) enters host cells and directs the assembly of new viruses; radioactively labeled PROTEIN with 35S methionine and DNA with 32P phosphate… infected E.coli then sheared off phage with a blender… followed the isotopes in the infected bacteria to see that the 32P entered the cells during infection but not the 35S

45
Q

lytic cycle

A

phage quickly replicates and kills host cell; generally occurs when host cell conditions are good or very bad; bacteria divide quickly but the phage replicates even faster

46
Q

lysogenic cycle

A

phage is quiescent: may integrate into host cell genome and replicate only when host genome divides; generally occurs in moderate cell conditions; phage can reactivate to become lytic and kill host

47
Q

lysogenic conversion

A

when a bacterium acquires a new trait from its temperate phage; virus assumes a host cell toxin and the virus can thus produce toxins

48
Q

(bacteriophage) synthesize capsids

A

using host cell components

49
Q

(bacteriophage) exit from host cell

A

lysis or slow release

50
Q

lysis

A

makes protein to depolymerize peptidoglycan and bursts host cell to release progeny phage

51
Q

slow release

A

filamentous phages can extrude individual progeny through cell envelope

52
Q

eukaryotic virus life cycles

A
  1. ATTACHMENT to host cell receptor… 2. ENTRY into cell… 3. genome REPLICATION… 4. ALL VIRUSES MAKE PROTEINS WITH HOST RIBOSOMES… 5. ASSEMBLY of new viruses… 6. RELEASE of progeny viruses from host cell
53
Q

(eukaryotic virus) entry into cell

A

injects genome directly; or taken up via endocytosis (VIROPEXIS): brought into cell in an endosome; or fuses envelope to plasma: releases capsid into cytoplasm

54
Q

viropexis

A

Virus penetration/entry into cell by way of phagocytotic engulfment of viral particle into endosome via endocytosis

55
Q

entry into a cell of a naked eukaryotic virus

A

can only occur through viropexis

56
Q

entry into a cell of an enveloped eukaryotic virus

A

can occur through viropexis or fusion of envelope to plasma membrane of host cell

57
Q

(eukaryotic virus) genome replication

A

DNA VIRUSES MUST GO TO CELL NUCLEUS (to use host polymerase or replicate in cytoplasm with viral polymerase); RNA VIRUSES MUST ENCODE A VIRAL POLYMERASE (tend to stay in cytoplasm with ribosomes because host cells cannot read RNA to make more RNA); ONLY (+)ssRNA CAN BE USED AS mRNA [dsRNA and (+)ssRNA genome can be translated, but (-)ssRNA and retrovirus genomes must be replicated to be translated]

58
Q

(eukaryotic viruses) all viruses make proteins with host ribosomes

A

translation occurs in cytoplasm

59
Q

(eukaryotic viruses) assembly of new viruses

A

capsid and genome; assembly may occur in cytoplasm or in nucleus; capsid proteins must move into the nucleus and envelope proteins are inserted into host membrane

60
Q

(eukaryotic viruses) release of progeny viruses from host cell

A

lysis of cell (similar to bacteria) or BUDDING

61
Q

budding

A

virus passes through membrane; membrane lipids surround capsid to form envelope

62
Q

all enveloped viruses

A

bud from a membrane

63
Q

culturing viruses - general amount of phages/mL at each phase

A
  1. VIRUSES BOUND TO HOST – free virus concentration drops… 2. ECLIPSE PERIOD – viruses making proteins, genomes, assembly; free virus concentration remains the same… 3. RAPID RISE PERIOD – burst of bacteriophage in bacterial lysis or rapid release of eukaryotic viruses increases free virus concentration
64
Q

culturing viruses on plates

A

viruses grown with host cells as food (bacteria in culture, animal cells in tissue culture); host cells form confluent lawn (viruses from PLAQUES where host cells are killed)

65
Q

plaque

A

“colony” of viruses; the hole in the confluent lawn where all cells died from virus replication “eating” cells

66
Q

viral ecology

A

viruses present in ALL ENVIRONMENTS often at very HIGH DENSITIES; viruses limit population host density; viruses increase host diversity (strong selection for virus-resistant strains); people susceptible if exposed to a new virus (West Nile Virus, smallpox virus in new world)

67
Q

restriction

A

general host mechanism to prevent invasion from viral DNA through destruction of foreign DNA by cleaving with enzymes

68
Q

viroids

A

JUST NUCLEIC ACID: NAKED (single stranded) RNA; plant pathogens; circles and very small (100-300 nucleotides); a subviral particle that is only genetic material

69
Q

prions

A

JUST PROTEIN; animal pathogens; “slow viruses” – spongiform encephalopathy, kuru, mad cow disease, CREUTZFELD-JAKOB DISEASE, DEFECTIVELY FOLDED HOST PROTEIN; subviral particle that is only protein shell

70
Q

spongiform encephalopathy

A

degeneration of neurons – abnormal folding causes longer neurotransmitter trafficking, causing neurons to die and leave holes in neural material

BIO 286 - Microbiology (21 decks)

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