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microbiology final > chapter 5 - viruses > Flashcards

chapter 5 - viruses Flashcards

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Biology 101 flashcards
1
Q

What is a virus

A

genetic element that can only multiply in a host cell

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2
Q

What are viral components of a naked particle

A

nucleic acids and capsid

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3
Q

What are viral components of a enveloped virus

A

glycoprotein, nucleocapsids and envelope

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4
Q

What are the two modes of infection?

A

virulent: gets into cell, makes copies, then bursts
lysogenic: gets in cell, stays in genome and comes out when it wants

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5
Q

What is a virion?

A

extracellular form of a virus, facilitates transmission

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6
Q

What is a capsomere

A

protein molecules arranged around nucleic acid making capsule capsids

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7
Q

What are the two basic virus symmetry?

A

helical: rod shaped, length determines by nucleic acid, width is the size of capsomere.
Icosahedral: spherical, requires few capsomere

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8
Q

What does structural integrity mean

A

provides structure and shape

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9
Q

What does the complex viral structure intel?

A
  • head (contains DNA)
  • collar
  • tail
  • tail fibers
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10
Q

What are the enzymes inside virions and what are their roles?

A
  1. lysozymes: makes hole in the bacteria to allow entry of nucleic acid
  2. neuraminidase: destroys glycoproteins/lipids and allows liberation of viruses.
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11
Q

What are the two types of nucleic acid polymerases?

A
  1. RNA replicase: RNA-dependent RNA polymerase
  2. Reverse transcriptase: RNA-dependent DNA polymerase in retrovirus
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12
Q

What are enveloped viruses?

A

nucleocapsid surrounded by lipoprotein membrane, use outer surface proteins to attach/insert.

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13
Q

What is a plaque assay?

A

clear zones of cell lysis that developed on lawns of host cells where successful viral infections occur

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14
Q

What is a titer?

A

number of infectious virions per volume of liquid

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15
Q

What are the three steps of culturing viruses?

A
  1. cell-phage mixture is poured onto a solidified nutrient agar plate.
  2. mixture is left to solidify
  3. incubation allows bacterial growth and phage reproduction
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16
Q

What is plating efficiency?

A

estimates of viral titer by plaque assay

17
Q

What are the 5 steps of the replication cycle of prokaryotic viruses?

A
  1. Attachment: absorption of virus
  2. Penetration: entry/injection of viral nucleic acid
  3. Synthesis: of viral nucleic acid + proteins by host cell as redirected virus
  4. Assembly: of capsids + packaging of viral genomes into new virions
  5. Release: of new virions from host.
18
Q

What is the eclipse phase?

A

genome replicated + proteins synthesized

19
Q

What is the maturation phase?

A

packaging nucleic acids in capsids (proteins being made)

20
Q

What is the latent period?

A

eclipse + maturation phase

21
Q

What does burst size mean?

A

number of virions released

22
Q

During virions synthesis, what proteins are needed?

A
  1. Early proteins: enzymes needed for DNA replication + proteins that modify host enzyme
  2. Middle + late proteins: head + tail proteins and enzymes required to liberate mature phages
23
Q

What are the 3 stages of packaging virions?

A
  1. Prohead gets assembled
  2. Motor assembles
  3. Genome gets pumped into prohead using ATP
24
Q

What are the two pathways in temperate bacteriophages?

A
  1. Lytic Pathway
    - after attachement/injection, lytic events are initated
    - phage synthesized and virions assemble
    -lysis of host cell, release of new virion
  2. Lysogenic Pathway
    - after attachment/injection, viral DNA is integrated into host DNA
    -cell becomes lysogenized
    - viral DNA replicated with host DNA
    - prophage is created
25
Q

What are the similarities of animal/bacterial viruses?

A
  1. capsids + DNA/RNA genome
  2. Infection and takeover of host
  3. assembly and release
26
Q

What are the differences of animal/bacterial viruses?

A
  1. entire virion enters animal cell
  2. eukaryotic cell contains nucleus + site reproduction
  3. viroplasms form in some eukaryotic cells to increase virion assembly rate.
27
Q

What are the outcomes of virulent infections?

A
  1. Transformation: normal cell - tumor cell
  2. Persistent: slow release of virions from host cell (no lysis)
  3. latent infection: viral DNA exists in host genome as provirus (not active till triggered)
28
Q

What is a retrovirus?

A

enveloped virion that contains two ss(t) RNA genome

29
Q

Role of reverse transcriptase?

A

synthesize DNA from RNA

30
Q

Role of ribonuclease activity?

A

degrades RNA strands to DNA hybrid

31
Q

Role of DNA polymerase?

A

makes dsDNA from ssDNA using viral tRNA

32
Q

Role of integrase?

A

integrates dsDNA into genome

microbiology final (20 decks)

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