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Microbio 3220 > Exam 1 - Lecture 5 > Flashcards

Exam 1 - Lecture 5 Flashcards

1
Q

are viruses alive?

A

nah

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2
Q

what does a complete virion consist of?

A
  • nucleic acid (genome)
  • capsid (coat of protein)
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3
Q

what is a virus?

A

an infectious agent

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4
Q

true or false: viruses cannot exist extracellularly.

A

false, they can EXIST extracellularly but they can’t reproduce independent of a living host cell

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5
Q

what are some positives of viruses (what are some good things)?

A
  • important members of the aquatic world
  • important in evolution
  • important model systems in biology
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6
Q

a virus that infects bacteria is called a:

A

bacteriophage

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7
Q

virions are composed of:

A

RNA only

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8
Q

satellites are composed of:

A

nucleic acids (DNA/RNA) only

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9
Q

prions are composed of:

A

proteins only

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10
Q

viruses are composed of:

A

nucleic acid and protein (capsid)

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11
Q

what is the size range of virion diameter?

A

10-400 nm

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12
Q

true or false: virions can have both DNA and RNA.

A

false

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13
Q

what is the nucleocapsid of a virion?

A

nucleic acid and a protein coat (capsid)

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14
Q

what are the roles of capsids?

A
  • protect genetic material
  • aid in genetic transfer between host cells
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15
Q

what are the protein subunits of the capsid called?

A

protomers

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16
Q

what are the two common shapes of capsids?

A

helical and icosahedral (20 sides)

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17
Q

what are the subunits of an icosahedral capsid called?

A

capsomers

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18
Q

what are the largest animal viruses?

A

poxviruses

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19
Q

large bacteriophages have binal symmetry. what does this mean?

A

the head is icosahedral, the tail is helical

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20
Q

some viruses have another layer called an envelope. where does this usually come from?

A

host cell membranes

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21
Q

what are viral spikes?

A

viral encoded proteins that project from the envelope surface

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22
Q

what is an example of viral spikes that attach to the host cell?

what about spikes that have enzymatic activity?

A
  • hemagglutinin of influenza virus
  • neuraminidase of influenza virus
23
Q

what are the three enzymes found in HIV?

A
  • reverse transcriptase
  • integrase
  • protease
24
Q

true or false: viruses can have ssDNA genomes.

A

true

25
Q

true or false: viruses can have linear (noncircular) genomes.

A

true

26
Q

true of false: some viruses have 16S rRNA.

A

false, none do.

27
Q

what is the common gene between all viruses?

A

there is none!

28
Q

what are viruses that use reverse transcription called?

A

retroviruses

29
Q

what direction do you read genomes in?

A

5’ to 3’

30
Q

is the sense strand the plus- or negative-strand?

A
  • plus-strand

(idk why its plus and negative and not plus and minus or pos and neg)

31
Q

what are the seven Baltimore classification groups?

A

I: dsDNA
II: ssDNA (+)
III: dsRNA
IV: ssRNA (+)
V: ssRNA (-)
VI: ssRNA (RT) (+)
VII: dsDNA (RT)

RT means retrovirus

32
Q

what are the five steps of viral multiplication?

A
  1. attachment
  2. entry and genome uncoating
  3. synthesis
  4. assembly
  5. release
33
Q

how does attachment of the virus happen?

A

interaction between viral spikes (ligands) and the host cell receptors

34
Q

what is tropism?

A

tissue specific receptor distribution

35
Q

what are the three common methods of viral entry?

A
  • fusion of viral envelope with host membrane
  • endocytosis in a vesicle
  • injection of nucleic acid
36
Q

what is the synthesis stage of viral replication?

A

when the virion generates copies of itself

37
Q

which of the following have to bring their own proteins necessary for synthesis and cannot use the preexisting host machinery: dsDNA or RNA viruses?

A

RNA viruses

38
Q

true or false: all assembly takes place in the nucleus

A

false, some is in the nucleus, some in the cytoplasm, then they come together

39
Q

which will lyse the cell upon release: enveloped or nonenveloped viruses?

how do they do it?

A
  • nonenveloped viruses
  • they have holin to create pores in the plasma membrane OR lysozymes that degrade peptidoglycan
40
Q

how are enveloped viruses released from the cell?

A

budding: an envelope is derived from the host cell membrane

41
Q

which form of viral release allows for the host cell to survive and continue releasing virions for some time?

A

budding

42
Q

what is the name of the virus that causes COVID-19?

A

SARS-CoV-2

43
Q

what does SARS stand for?

A

severe acute respiratory syndrome

44
Q

what kind of genome does SARS-CoV-2 have?

where does that put it on the Baltimore classification system?

A
  • ssRNA (+) genome
  • group IV
45
Q

what are the two receptors that SARS-CoV-2 binds to?

A

ACE2 and TMPRSS2

46
Q

virulent phages ________ immediately upon entry. then, they _____ the bacterial host cell

A

multiply; lyse

47
Q

what is a lysogenic relationship?

A

when a virus integrates its genome into the host’s genome so that whenever the host replicates it’s genome, the virus’ genome is replicated too (lysogenic cycle)

when it’s done doing that, it enters the lytic cycle (lysing of the cell)

48
Q

what are some of the advantages of lysogeny?

A
  • bacteria immune to superinfection
  • phages may give bacteria beneficial genes
  • viruses are ensured to survive in the presence of other phages
49
Q

what does cytocidal infection of eukaryotic cells lead to?

A

death of the cell through lysis

50
Q

if bacteria is grown in media, will the media increase or decrease in turbidity when infected with a virus?

A

decrease, because the virus will kill the bacteria

51
Q

what is a PFU in a plaque assay?

A
  • plaque-forming units
  • 1 plaque = 1 virion = 1 PFU
  • each individual phage its own plaque
52
Q

if there is 10x less virus in a diluted solution, there will be _______ plaque

A

10x less plaque

53
Q

what diseases do prions cause in humans and animals? what are some examples?

A

neuro-degenerative diseases
- Scrapie in sheep
- Bovine spongiform encephalopathy (mad cow disease)
- Kuru, Creutzfeld-Jakob disease

54
Q

how do prions change proteins to cause disease?

A

cellular proteins are present in normal forms, but prions are present in abnormal forms. prions cause normal protein to change into abnormal proteins, and this cascades

Microbio 3220 (24 decks)

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