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Microbiology > Viruses > Flashcards

Viruses Flashcards

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Biology 101 flashcards
1
Q

General characteristics

A

-obligate intracellular paracites
-acellular
-have either DNA or RNA
have protein coat
-no ribosomes
-no ATP-generation
-no enzymes
-20-1000 nm (only seen with e microscope)

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2
Q

host range

A

the spectrum of host cells a virus can infect

  • most infect specific types of cells in host
  • determined by attachment cites and cellular factors
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3
Q

DNA viruses

A

single or double stranded, linear or circular

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4
Q

RNA viruses

A

linear, single or double stranded, one molecule or segmented

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5
Q

capsid

A

protein coat around nucleic acid

  • made of capsomeres = 1 protein or multiple dif ones
    function: carries NA from cell to cell, protects NA from nucleases, attaches to cell receptors (naked viruses), is antigenic
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6
Q

envelope

A

surrounds nucleocapsid of some animal viruses

  • made of host cell lipids and viral proteins
  • lipid bilayer sourounding capsid
  • spikes are antigenic and aid in attachment
  • can change viral proteins to avoid antibiotics
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7
Q

Types of viral morphology

A
  • helical
  • polyhedral
  • enveloped
  • complex
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8
Q

helical viruses

A

nucleic acid spirals

-many copies of the same protein wrapped in helical conformation with NA inside

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9
Q

polyhedral viruses

A
  • icosahedral = 20 sides and each side is an equilateral triangle
  • adenovirus
  • polio
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10
Q

enveloped virus

A

-dif shapes on the inside, but apperes spherical bc of envelope

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11
Q

complex viruses

A
  • capsid head w/ NA
  • sheath
  • base plate
  • tail fiber
  • pin
  • e.g. phage or orthopoxvirus
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12
Q

taxonomy

A
  • genus = -virus
  • family = -viridae
  • order = -ales
  • species = common name
  • sub species = a number

species = viruses that share some genetic info and ecological niche (host)

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13
Q

Why are viruses typically grown in bacteria in lab

A

bc it is the cheapest way—> bacteria need living host

-bacteriophages form plaques on lawn –> PFU

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14
Q

3 ways of growing animal virus in lab

A
  1. in living animal
  2. in embryonated eggs
  3. in cell cultures
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15
Q

growing bacteria in cell cultures

A
  • treat tissue with enzyme that separates cells
  • put cells in growth solution
  • virally infected cells are detected via deterioration (cytopathic effect
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16
Q

continuous cell lines

A

normal cells grow in monolayer + adhere to glass

infected ones stack up

17
Q

viral identification

A
  • cytopathic effect
  • serological testing (western blotting = reaction of virus with antibodies)
  • Nucleic acids –> PCR
18
Q

requirements for viral multiplication

A

must infect host

must override host’s metabolic machinery

19
Q

one-step growth curve

A
  • eclipse period
  • virions released from host cell
  • acute period
20
Q

lytic life cycle

A
  • tail fibers recognize attachment site
  • virion squats down
  • lysozyme on tail fiber hydrolyzes cell wall
  • tail sheath contracts
  • tail core goes through cell wall
  • DNA is injected
  • capsid stays outside
  • transcription of viral DNA
  • translation of viral mRNA
  • no more host DNA or protein synthesis
  • assembly of phage particles
  • phage lysozyme breaks cell wall + releases virions
21
Q

lysogenic life cycle

A
  • starts same as lytic, but viral DNA is incorporated into host chromosome
  • viral DNA = prophage
  • host replicates its own chromosome with prophage
  • Phage conversion = host cell exhibits new properties (only if 1 or more phage gene is expressed)
  • host cell immune to re-infection by same virus
  • can be responsible for specialized transduction
22
Q

Steps of animal virus multiplication

A
  1. attachment
  2. penetration
  3. uncoating
  4. biosynthesis
  5. maturation
  6. release
23
Q

attachment/absorption (animal)

A
  • attach through receptors on host cell’s surface (proteins and glycoproteins on membrane)
  • viral particles have spikes or fibers that bind
  • naked viruses have attachment sites on nucleocapsid
  • enveloped viruses have them on envelope
24
Q

penetration / uncoating

A
  • enveloped viruses fuse with outer membrane of host
  • naked viruses’ capsids degrade on outer membrane
  • Both use receptor-mediated-endocytosis
25
Q

Where is viral DNA, RNA, and capsids synthesized in host?

A
  • nucleus
  • cytoplasm
  • cytoplasm
26
Q

RNA viruses that use DNA

A

Ex: retroviridae:

  • attach with peplomers
  • penetrate with fusion
  • RNA is converted to DNA via reverse transcriptidase (RNA dependant DNA polymerase)
  • DNA goes to nucleus where it integrates into host DNA and it expressed
  • normal biosynthesis, maturation, and release via budding
27
Q

virus release

A
  • naked viruses usually lyse the host cell and kill it

- enveloped viruses bud –> take cell membrane as envelope

28
Q

How viruses cause disease

A
  • lyse cells
  • break chromosomes
  • change cell’s surface
  • shrink the cell
  • form vacuoles in cell
  • promote apoptosis
  • promote fusion
  • cause cells to fuse –>polykaryocyte
29
Q

burst time

A

length of time from attachment to release

30
Q

burst size

A

number of particles released from cell 50-200

31
Q

oncogenes

A

transform normal cells into cancerous ones

32
Q

oncogenic viruses

A
  • incorporate into host cell DNA and induce tumors

- transformed cell has tumor-specific-transplantation-antigen on surface and is irregularly shaped

33
Q

latent viral infections

A
  • asymptomatic for a long time
  • may reactivate due to changes in immunity
  • cold sores, shingles
34
Q

persistent viral infections

A
  • occurs gradually over long period and is usually fatal

- measles

35
Q

Antiviral drugs

A
  • Not antibiotics
  • entry and fusion blockers –> block receptors on virus
  • prevent viral uncoating (not used bc resistance)
  • inhibit viral DNA integration to host DNA
  • nucleoside analogs inhibit viral DNA or RNA synthesis
  • interference with assembly and release of viral inhibitors
  • exit inhibitors —> inhibit neuraminidase used for budding
36
Q

Protease inhibitors

A

block cleavage of viral protein precursors

37
Q

Prions

A

-Proteinaceous infectious particles
-inherited and transmissible by ingestion, transplant, and surgical instruments
-not viruses
-not living
-messed up protein that messes up other proteins
spongiform encephalopathies

Microbiology (15 decks)

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