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Virology > Viral Structure and Composition > Flashcards

Viral Structure and Composition Flashcards

1
Q

What is the smallest virus?

A

Porcine circovirus type 1 (17nm)
Parvo (18nm)

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2
Q

What is the largest virus

A

Pandoravirus (400nm)
Poxvirus (200nm) animal & human

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3
Q

Shape and example

A

Filament, Ebola

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4
Q

Shape, example

A

Bullet, Rabies

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5
Q

Shape, example

A

Tadpole, Bacteriophage

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6
Q

Shape, example

A

Rod, Tobacco Mosaic Virus

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7
Q

Shape, example

A

Brick, Poxvirus

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8
Q

Shape, example

A

Spherical, Rotavirus

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9
Q

Pleomorphism

A

ability of virus to alter shape or size

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10
Q

Electron microscopy use?

A

Low resolution, virus MUST have distinct morphology to view, requires staining (50-75 angstroms)

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11
Q

Cryo-electron Microscopy

A

Uses liquid nitrogen to freeze virus and increase resolution (3.3-20 angstroms)

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12
Q

X-Ray Crystallographic Method

A

virus protein crystallized and hit with x-rays, angles of refraction show detailed structure

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13
Q

Nuclear Magnetic Resonance

A

electromagnetic radiation hits virus and reflect to give shape - MOST DETAILED

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14
Q

Virus Morphology

A

1.) Genes
2.) Capsid
3.) Envelope (may be absent)
4.) protein molecules

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15
Q

Describe a capsid

A

protein shell of a virus, encases viral nucleic acid or genome

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16
Q

What is a capsid made of?

A

Capsomeres held by non-covalent bonds

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17
Q

How many capsids do viruses usually have? What is the exception?

A

One, Rotavirus has 2

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18
Q

List components of a nucleocapsid

A

capsid + nucleic acid/genome

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19
Q

Types of capsid symmetry

A

Helical, cubic/icosahedral, complex

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20
Q

Helical symmetry

A

spring shaped, capsid added like spiral staircase - CANNOT FORM INCOMPLETE VIRIONS

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21
Q

Enveloped Helical Viruses are what type?

A

ALL ANIMAL VIRUSES

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22
Q

Naked Helical Nucleocapsids are what type?

A

plant viruses
(tobacco mosaic virus)

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23
Q

Cubic Symmetry

A

Geometric with 2 capsomere types: hexagonal and pentagons

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24
Q

How many pentons are in icosahedral symmetry? Hexagons?

A

ALWAYS 12 - hexagons vary

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25
Q

What is the Triangulation Number?

A

relation between # pentagons and hexagons

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26
Q

What does larger triangulation number mean?

A

more hexagons relative to pentagons

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27
Q

Triangulation Number Equation

A
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28
Q

Naked Icosahedral

A

lacks lipid envelope

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29
Q

Enveloped Icosahedral

A

possesses lipid envelope

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30
Q

Describe Parvovirus capsid

A

Simplest icosahedron T=1, 60 CP protein copies

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31
Q

Describe Reoviridae capsid

A

Outer: T=13 icosahedral
Inner: T=2 icosahedral

32
Q

Complex Symmetry

A

several parts with several shapes and symmetries

33
Q

Complex symmetry examples

A

Pox Virus, Bacteriophages

34
Q

Functions of Capsid (8)

A

1.) Structural Symmetry
2.) Protection (enzyme, chem, envir)
3.) Receptor attachment to host
4.) Interaction w/ host membrane
5.) uncoating viral genome at right site
6.) transport viral genome to site
7.) facilitate specific recognition and genome packaging
8.) determines antigenicity via antigenic sites

35
Q

What is a lipid envelope?

A

lipid bilayer with embedded proteins that surrounds a virus

36
Q

How does a envelope assist a virus

A

facilitates entry, adaptation and evasion of host immune system

37
Q

T/F: enveloped viruses can cause persistent infections

A

True

38
Q

Process of acquiring envelope

A

Budding

39
Q

Budding Process

A

1.) Virus specific proteins in host membrane
2.) virus buds and encloses self in stolen host membrane

40
Q

What membranes can an envelope come from?

A

Cytoplasmic, organelle membranes (golgi, ER, nuclear)

41
Q

Two kinds of viral proteins in envelope?

A

Glycoprotein and Matrix protein

42
Q

What are the two types of glycoproteins?

A

External glycoprotein and Channel proteins

43
Q

Describe External Glycoprotein

A

Major Ag of viruses, involved in hemagglut, receptor binding, antigenicity, membrane fusion

44
Q

Describe Channel Proteins

A

hydrophobic, form protein lined channel
TARGET FOR DRUGS

45
Q

Channel protein function

A

alters permeability of membrane and modifies internal viral environment

46
Q

Fusion gylcoproteins

A

role in infection of enveloped virus

47
Q

Envelope Matrix Protein function (6)

A

1.) link internal nucleocapsid and envelope
2.) crucial for viral assembly
3.) stabilizes lipid envelope
4.) interact w/ RNP complex
5.) nucleocapsid recognition site - mediates encapsulation of RNA into envelope

48
Q

In what environment is an envelope maintained?

A

aqueous or moist

49
Q

What is an envelope sensitive to?

A

desiccation, heat, pH change

50
Q

How do you inactivate a envelope?

A

lipid solvents (ether, chloroform, sodium deoxycholate, detergents)

51
Q

Are enveloped viruses easy to sterilize?

A

YES, cannot survive in environment for long periods of time

52
Q

Which is not a component of a virus?
A. nucleic acid
b. capsid
c. envelope
d. capsule

A

D. capsule - this is a bacterial component

53
Q

Where is the viral matrix protein located?

A

between capsid and envelope

54
Q

What is positive sense RNA virus

A

infectious genome, can be immediately translated by the host cell 5-3 direction

55
Q

What is negative sense RNA virus?

A

noninfectious genome, 3-5 direction must be converted to positive sense before translation

56
Q

What is Antigenic Drift and outcomes?

A

Mutations
minor changes, antiviral resistance, change antigenicity

57
Q

Silent mutation

A

no change in protein coding

58
Q

Nonsense mutation

A

changes to stop codon

59
Q

missense mutation

A

changes overall protein coding to different protein

60
Q

Antigenic Shift types

A

Recombination and Reassortment

61
Q

Describe Recombination

A

exchange of nucleotide sequence between different but closely associated viruses

62
Q

In what type of virus does recombination occur?

A

in a virus with ONLY ONE GENE SEGMENT or ONE SEGMENT of multi-segment virus

63
Q

Describe Reassortment

A

various segments can be exchanged between viruses

64
Q

What is the most important mech for genetic diversity in viruses?

A

Reassortment

65
Q

In what type of viruses does reassortment occur?

A

multi-segmented genome ONLY

66
Q

What is Retroviral integrase (IN)

A

enzyme from retrovirus that enables genetic material to be inserted into host genome

67
Q

What is reverse transcriptase (RT)

A

enzyme used to generate complimentary DNA from RNA template

68
Q

What is nucleic acid polymerases

A

photocopy machine of parent genome for viral genome replication

69
Q

Lysins

A

enzymes produced by bacteriophages to cleave host walls

70
Q

Neuraminidases

A

allows viral release from host cell

71
Q

What are Viral nonstructural proteins?

A

role in viral replication, regulation or assembly, prevent host interference with replication

72
Q

When are nonstructural proteins present?

A

only during replication inside host cell - WILL NEVER SEE OUTSIDE HOST CELL

73
Q

What is an incomplete virion?

A

virion without nucleic acid
only an empty capsid

74
Q

Describe and defective virions?

A

cannot replicate, lacks full copy of viral genes due to mutations or errors

75
Q

When does replication of defective virions occur?

A

mixed infections with a helper virus

76
Q

What is a pseudovirion?

A

contains non-viral genome, usually host nucleic acid
look like virus but DO NOT REPLICATE

77
Q

What is a pseudotype?

A

when related viruses infect same cell, genome of one virus may be closed in capsid of other virus

Virology (3 decks)

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