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MSI: Unit 3 Immuno/Micro > Virus Structure, Classification, and Life Cycle > Flashcards

Virus Structure, Classification, and Life Cycle Flashcards

1
Q

What are filterable agents and how did the name come about?

A

Filterable agents are viruses. The name came about when these organisms could filter through 220nm pores. Hence, bacteria are bigger than 220nm while viruses are smaller than 220 nm because bacteria were trapped by the filter and filtrate was not infectious while the viruses went thru and filtrate remains infectious.

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2
Q

Order in terms of size from largest to smallest, ribosomes, atoms, proteins, viruses, animal cells, plant cells, eyes, bacteria

A
  1. eyes
  2. plant cells
  3. animal cells
  4. bacteria
  5. viruses
  6. ribosomes
  7. proteins
  8. atoms
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3
Q

T/F: viruses are associated with all life forms

A

True

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4
Q

Definition of a virus

A

a capsid-encoding organism that has a genome

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5
Q

what is a capsid?

A

protein shell that encapsulates the nucleic acid genome

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6
Q

what is a virion?

A

the particle encoded by a virus genome

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7
Q

All viruses have these 3 basic gene modules

A
  1. capsid proteins
  2. replicon (encodes the nucleic acid polymerase and accessory proteins to copy the genome)
  3. host-cell interacting factors
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8
Q

What are the non-structural and structural proteins in viruses?

A

non-structural proteins = host-cell interacting factors

structural proteins = capsid proteins

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9
Q

Virions contain which basic gene modules

A

genome and capsid

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10
Q

T/F: The capsid shape and genome type are dependent

A

False: the capsid shape and genome type are independent

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11
Q

What are 3 ways to classify viruses?

A
  1. host cell (kingdom)
  2. genome type (RNA or DNA; single or double stranded)
  3. virion structure (enveloped or naked; icosahedral, helical or complex)
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12
Q

State the genome type, the structure and whether it’s enveloped or not: Adenovirus

A

1 -dsDNA

  1. icosahedral
  2. naked
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13
Q

State the genome type, the structure and whether it’s enveloped or not: Poxvirus

A
  1. dsDNA
  2. complex
  3. enveloped
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14
Q

State the genome type, the structure and whether it’s enveloped or not: Influenza Virus

A
    • segmented RNA
  2. helical
  3. enveloped
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15
Q

State the genome type, the structure and whether it’s enveloped or not: Herpesvirus

A
  1. dsDNA
  2. icosahedral
  3. enveloped
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16
Q

State the genome type, the structure and whether it’s enveloped or not: Retrovirus

A
    • ssRNA (2 copies b/c diploid)
  2. icosahedral
  3. enveloped
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17
Q

All viruses share this simple 3-part strategy to ensure their survival

A
  1. The genome encodes a capsid that protects it outside the cell
  2. The genome contains info for infecting a cell, replicating the genome, intraceullar survival, and assembling virions
  3. Transmission to a new host is required to maintain the virus as a species
18
Q

What type of microscope is used to observe viruses and cell cultures?

A

Inverted microscopes because viruses are NOT visible by light microscopy

19
Q

Virus infection may cause ______________ that can be used to study virus replication and infectivity.

A

cytopathic effects

20
Q

What are 6 things viruses need to grow?

A
  1. The right host (tropism)
  2. Cells with the right receptors (susceptible)
  3. Appropriate intracellular environment (permissive)
  4. Biosynthetic machinery
  5. Abundant building blocks (RNA, DNA, amino acids, ATP, lipids, sugars, etc.
  6. Time to finish replication
21
Q

What are the 9 general steps in virus replication?

A
  1. Recognition
  2. Attachment
  3. Entry: Penetration or Fusion
  4. Cell coating
  5. Transcription, making more mRNA
  6. Protein translation
  7. Replication of the genome
  8. Assembly of virions
  9. Egress: lysis, budding, or exocytosis
22
Q

Define host range

A

The preferred species

23
Q

Define abortive infection

A

replication is incomplete

24
Q

Define tissue tropism

A

the preferred cell type

25
Q

Which step of viral replication marks the beginning of eclipse phase?

A

Uncoating

26
Q

Viruses can uncoat in these regions

A

At the plasma membrane, within endosomes, at the nuclear pore

27
Q

T/F: All viruses must make mRNA

A

True

28
Q

T/F: Only host transcription factors regulate transcription of viral genome

A

False; both viral and host transcription factors regulate mRNA synthesis

29
Q

Viral mRNAs are translated into protein by host machinery, requiring these 3 host components

A
  • ribosomes
  • tRNAs
  • Amino acids
30
Q

How are viral proteins sorted?

A

They are sorted to site of virion assembly. Capsid proteins interact with newly made genomes. Membrane proteins traffic thru secretory pathway and cytosolic proteins accumulate next to membrane

31
Q

T/F: Polymerases make new genomes using host cell nucleotides

A

True

32
Q

Which polymerase is unique to viruses?

A

RNA-dependent RNA polymerase (RDRP) -makes mRNA and genomes

33
Q

What marks the end of eclipse phase?

A

Assembly of virions so eclipse phase is from uncoating of capsid to assembling of virions

34
Q

Do viral DNA get inserted into capsid as it’s growing or after the capsid has been made.

A

Viral DNA is inserted after the capsid shell has been made already.

35
Q

Where do enveloped viruses acquire their lipid bilayer?

A

membranes from ER, Golgi, Plasma membrane

36
Q

T/F: All virion components accumulate at the site of capsid formation, genome incorporation, matrix, glycoproteins, and envelopment

A

True

37
Q

How can virions transfer to new cells?

A

by syncytium formation

38
Q

The entry of enveloped viruses into cells involves

A

fusion between viral and cellular membranes

39
Q

T/F: Virion envelopes are constructed from viral glycoproteins and host membranes

A

True

40
Q

T/F: Exocytosis of enveloped virions occurs in a burst and lyses the cell.

A

False

MSI: Unit 3 Immuno/Micro (16 decks)

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