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Microbiology > Virology > Flashcards

Virology Flashcards

1
Q

What can viruses infect?

A
  • plants
  • animals
  • bacteria
  • fungi
  • other viruses

A virus that infects bacteria won’t infect any other thing

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2
Q

What are the differences between deasd and alive viruses?

A

Dead
1. inert
2. no cell compounds
3. no metabolism
4. no autonomy

Alive
1. Nucleic aicd
2. proteins
3. mutate
4. grow and multiple
5. react

Inert= onactive when not in a host
No autonomy= cannot survive on their own

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3
Q

True or false

All viruses have a nucleic acid and a protein coat

A

True

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4
Q

What is the structure of a virus?

A
  1. Nucleic acid
    • encodes virus genes
  2. protein coat
    * protective
    * enzymatic
  3. envelope (lipid bilayer)
    * matrix protein

Spikes attach to receptor sites on host cells. Phages attach by tail fibers.
Enveloped viruses have a lipid bilayer obtained from a host cell.
Enveloped viruses are more susceptible to disinfectant because damage to the envelope does not allow them to infect

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5
Q

What are the 3 shapes of viruses?

A
  1. Icosahedral
  2. helical
  3. complex
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6
Q

What is the description of a icosahedral shape?

A

20 flat triangles

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7
Q

What is the description of a helical shape?

A

capsomeres arranged in helix

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8
Q

What is the description of a complex shape?

A
  • phage
  • icosahedral nucleocapsid (head)
  • helical protein (tail)
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9
Q

What are bacteriophages?

A
  1. infect bacteria
    * lytic
    * temperate
    * filamentous

bacteriophages enter and leave the bacteria via the F pilus
exit the host by lysing the cell

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10
Q

What is lytic?

A

lyse the host cells and then end of infection

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11
Q

What is temperate?

A

lytic or lysogenic

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12
Q

What is filamentous?

A
  • rod shaped
  • requries an F-pilus
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13
Q

What is horizontal gene transfer in bacteriophages?

A

Transduction
* generalized
* specialized

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14
Q

What is generalized horizontal gene transfer?

A
  • Bacterial DNA that has been degraded can accidently packaged with new phage heads
  • Some viruses contain only fragmented bacterial DNA, these viruses cannot drive replication, but can incorporate into newly infected cell
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15
Q

What is specialized horizontal gene transfer?

A
  • Bacterial DNA is excised with virus DNA when going from lysogenic to lytic
  • When incorporated into Phage it is defective, can also be incorporated into targets DNA
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16
Q

What is a bacteriophage?

A

a virus that infects bacteria

17
Q

What is a capsomere?

A

proteinaceous subunit of a capsid

some capsomeres are composed of only a single type of protein, whereas others are composed of several different kinds of proteins.

18
Q

What is present in a viruses extracellular state?

A

virions have capsids-protein coats that provide both protection for viral nucleic acid and a means by which many viruses attach to their hosts’ cells.

19
Q

What is a capsid made of?

A

capsomeres

20
Q

What is a nucleocapsid?

A

nucleic acid surrounded by a capsid

21
Q

What are the three basic shapes of virions?

A

Helical, polyhedral, and complex

22
Q

True or False?

All viruses lack cell membranes

A

True

23
Q

True or False

Animal viruses have an envelope similar in composition to a cell membrane surrounding their capsids

A

True

24
Q

What is a virion called when it lacks an envelope?

A

non-enveloped or naked

25
Q

What are the 5 steps of the animal virus infection cycle?

A
  1. attachment (absorption)
  2. genome entry
  3. synthesis
  4. assembly
  5. release
26
Q

What happens in a lytic replication cycle?

A
  1. Attachment of the virion to the host cell
  2. Entry of the virion or its genome into the host cell
  3. Synthesis of new nucleic acids and viral proteins by the host cell’s enzymes and ribosomes
  4. Assembly of new virions within the host cell
  5. Release of the new virions from the host cell
27
Q

Where are most DNA viruses located?

A

Nucleus

28
Q

Where do most RNA viruses develop?

A

solely in cytoplasm

29
Q

During viral replication, how are enveloped viruses released?

A

by budding

can result in persistent infections

30
Q

How are naked viruses released?

A

exocytosis or lysis

31
Q

What are acute infections?

A
  • Rapid onset; short duration
  • Burst of virions released from infected host cell
  • Immune system gradually eliminates virus
32
Q

What are persistent infections?

A
  • continue for years or lifetime
  • may or may not have symptoms

Can be chronic or latent

33
Q

What is a chronic infection?

A

continuous production of low levels of virus particles

carriers may lack symptoms, but still transmit the virus

34
Q

What is a latent infection?

A

viral genome remains silent in host cell; can reactivate to cause productive infection

35
Q

What is a prion?

A

are proteinaceous infectious agents
* Linked to slow, fatal human diseases; animal diseases
* Usually transmitted only within a species
* Composed solely of protein; no nucleic acids

36
Q

What are the characteristics of prions?

A

Cellular PrP
* made by all mammals
* normal, functional structure has α-helices
Prion PrP
* Disease-causing form has β-pleated sheets
* Prion P r P causes cellular P r P to refold into prion P r P

37
Q

True or False

Normal sterilization procedures do not deactivate prions

A

True

38
Q

How are prions destroyed?

A

Prions destroyed by incineration or autoclaving in concentrated sodium hydroxide

Microbiology (15 decks)

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