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microbiology > ch. 5 - intro to viruses > Flashcards

ch. 5 - intro to viruses Flashcards

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Biology 101 flashcards
1
Q

what is the vital role of viruses?

A

are obligate intracellular parasites
- cannot multiply unless they invade a specific host cell + instruct its genetic and metabolic machinery to make and release new viruses

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2
Q

are viruses alive?

A
  • they are described as active or inactive
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3
Q

what is virus latin for?

A
  • means poison in latin
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4
Q

what are the three things that classify a virus?

A

1) is infectious
2) host cell takes care of all needs
3) have own genetic material - either DNA or RNA

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5
Q

what are the parts needed for a virus to invade and control a host cell?

A
  • spikes: target
  • capsid: external coating
  • genetic material (either DNA or RNA)
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6
Q

what is the capsid?

A
  • protein shell that surrounds the nucleic acid
    nucleocapsid - the capsid together with the nucleic acid
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7
Q

what is a naked virus?

A
  • consists only of a nucleocapsid
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8
Q

what is the envelope?

A
  • external covering of nucleocapsid - usually modified piece of host’s cell membrane
  • during budding
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9
Q

what are the spikes?

A
  • found on naked or enveloped viruses
  • project from nucleocapsid or envelope
  • allow viruses to dock with host cells
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10
Q

what is a virion?

A
  • a fully formed virus able to establish an infection in a host cell
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11
Q

what are the three capsid shapes?

A
  • helical
  • icosahedral - 20 faces/12 corners
  • complex
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12
Q

what are the DNA viral genomes?

A
  • single-stranded DNA genomes
  • double stranded DNA genomes
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13
Q

what are the RNA viral genomes?

A
  • single-stranded RNA genomes
  • double-stranded RNA genomes
  • positive strand RNA viruses - have mRNA genomes
  • negative strand RNA viruses - have RNA strand complementary to mRNA
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14
Q

what are retroviruses?

A
  • RNA is replicated indirectly through a DNA using an reverse transcriptase enzyme
  • enzyme - takes RNA to DNA
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15
Q

steps to how a virus infects?

A

1) attachment - to host plasma membrane via spikes
2) penetration - uncoating is the separation of the capsid from the genome
3) synthesis - virus uses the host’s cellular machinery to make more of it own nucleic acid + protein
4) assembly - parts of the virus are put together in stepwise fashion
5) release - after new viruses are assembled, envelope proteins are incorporated into a cellular membrane —- virus then buds, taking membrane part with it as an envelope

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16
Q

what is a host range?

A
  • the limited range of cells that a virus can infect

ex.) – hep B - liver cells of humans
– poliovirus - intestinal + nerve cells of primates
– rabies - various cells of all mammals

17
Q

what is a tropism?

A
  • specificities of viruses for certain tissues
18
Q

what is endocytosis?

A
  • when the entire virus is engulfed by the cell + enclosed in a vacuole or vesicle
19
Q

what happens during uncoating?

A
  • enzymes in the vacuole dissolve the envelope and capsid
20
Q

what is it called when viral replication is normal?

A

lytic

21
Q

what is it called when viral replication when the virus stays in the host cell and replicates itself as the host cell replicates?

A

lysogenic - is hiding within host’s DNA

ex.) bacteriophage - infects and replicates only within bacteria

22
Q

what does CPEs mean?

A

cytopathic effects - virus-induced damage to the cell that alters its microscopic experience

ex.) - gross changes in shape + size
- development of intracellular changes
- inclusion bodies
- syncytia

23
Q

what are inclusion bodies?

A
  • compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm
24
Q

what is syncytia?

A
  • fusion of multiple host cells into single large cells containing multiple nuclei

ex.) respiratory syncytia virus (RSV)

25
Q

what are oncogenic viruses?

A
  • experts estimate that up to 20% of human cancers are caused by viruses
26
Q

what does transformation mean?

A

effect on the cell caused by oncogenic viruses

  • increased rate of growth
  • alterations in chromosomes
  • changes in cell’s surface molecules
  • capacity to divide for an indefinite period
27
Q

what are oncoviruses?

A
  • viruses capable of initiating tumors
28
Q

what are the two ways a virus can use living cells as their medium?

A
  • in vivo - laboratory-bred animals + embryonic bird tissues
  • in vitro - cell or tissue culture methods
29
Q

what are the primary purposes of viral cultivation?

A
  • isolate + identify viruses in clinical specimens
  • prepare viruses for vaccines
  • do detailed research on viral culture, multiplication cycles, genetics + effects on host cells
30
Q

what are two ways that viruses can cause cancer?

A

1) put themselves into a control gene - protooncogenic gene
2) take a control gene w/ it

31
Q

what is a plaque?

A
  • areas where virus-infected cells have been destroyed + show up as a clear, well-defined patches in the cell sheet

ex.) microscopic manifestation of cytopathic effects - CPEs

32
Q

treatment of viral infections?

A
  • antibiotics designed to disrupt prokaryotic cells have no effect on viruses
  • vaccines stimulate immunity
33
Q

what is an interferon?

A
  • occurs naturally in human cells
  • used with some success in treating and preventing viral infections
34
Q

what are viroids?

A
  • infectious RNA particles that can cause disease in crop plants
  • the replication cycle + disease causation process of viroids are not understood
35
Q

what are prions?

A
  • infectious proteins
  • bad version of prions can cause transmissible spongiform encephalopathies
    — in animals + humans
    mad cow disease = cow
36
Q

what can transmissible spongiform encephalopathies (TSEs) cause?

A
  • death of host from nerve cell death leading to sponge-like holes in brain tissue

symptoms: dementia, weakened muscles, loss of balance

human form called Creutzfeldt-Jakob disease (CJD)

37
Q

what are protooncogenes?

A
  • cells before cancer

microbiology (7 decks)

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