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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
What is the Triangulation Number?
relation between # pentagons and hexagons
26
What does larger triangulation number mean?
more hexagons relative to pentagons
27
Triangulation Number Equation
28
Naked Icosahedral
lacks lipid envelope
29
Enveloped Icosahedral
possesses lipid envelope
30
Describe Parvovirus capsid
Simplest icosahedron T=1, 60 CP protein copies
31
Describe Reoviridae capsid
Outer: T=13 icosahedral Inner: T=2 icosahedral
32
Complex Symmetry
several parts with several shapes and symmetries
33
Complex symmetry examples
Pox Virus, Bacteriophages
34
Functions of Capsid (8)
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
What is a lipid envelope?
lipid bilayer with embedded proteins that surrounds a virus
36
How does a envelope assist a virus
facilitates entry, adaptation and evasion of host immune system
37
T/F: enveloped viruses can cause persistent infections
True
38
Process of acquiring envelope
Budding
39
Budding Process
1.) Virus specific proteins in host membrane 2.) virus buds and encloses self in stolen host membrane
40
What membranes can an envelope come from?
Cytoplasmic, organelle membranes (golgi, ER, nuclear)
41
Two kinds of viral proteins in envelope?
Glycoprotein and Matrix protein
42
What are the two types of glycoproteins?
External glycoprotein and Channel proteins
43
Describe External Glycoprotein
Major Ag of viruses, involved in hemagglut, receptor binding, antigenicity, membrane fusion
44
Describe Channel Proteins
hydrophobic, form protein lined channel TARGET FOR DRUGS
45
Channel protein function
alters permeability of membrane and modifies internal viral environment
46
Fusion gylcoproteins
role in infection of enveloped virus
47
Envelope Matrix Protein function (6)
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
In what environment is an envelope maintained?
aqueous or moist
49
What is an envelope sensitive to?
desiccation, heat, pH change
50
How do you inactivate a envelope?
lipid solvents (ether, chloroform, sodium deoxycholate, detergents)
51
Are enveloped viruses easy to sterilize?
YES, cannot survive in environment for long periods of time
52
Which is not a component of a virus? A. nucleic acid b. capsid c. envelope d. capsule
D. capsule - this is a bacterial component
53
Where is the viral matrix protein located?
between capsid and envelope
54
What is positive sense RNA virus
infectious genome, can be immediately translated by the host cell 5-3 direction
55
What is negative sense RNA virus?
noninfectious genome, 3-5 direction must be converted to positive sense before translation
56
What is Antigenic Drift and outcomes?
Mutations minor changes, antiviral resistance, change antigenicity
57
Silent mutation
no change in protein coding
58
Nonsense mutation
changes to stop codon
59
missense mutation
changes overall protein coding to different protein
60
Antigenic Shift types
Recombination and Reassortment
61
Describe Recombination
exchange of nucleotide sequence between different but closely associated viruses
62
In what type of virus does recombination occur?
in a virus with ONLY ONE GENE SEGMENT or ONE SEGMENT of multi-segment virus
63
Describe Reassortment
various segments can be exchanged between viruses
64
What is the most important mech for genetic diversity in viruses?
Reassortment
65
In what type of viruses does reassortment occur?
multi-segmented genome ONLY
66
What is Retroviral integrase (IN)
enzyme from retrovirus that enables genetic material to be inserted into host genome
67
What is reverse transcriptase (RT)
enzyme used to generate complimentary DNA from RNA template
68
What is nucleic acid polymerases
photocopy machine of parent genome for viral genome replication
69
Lysins
enzymes produced by bacteriophages to cleave host walls
70
Neuraminidases
allows viral release from host cell
71
What are Viral nonstructural proteins?
role in viral replication, regulation or assembly, prevent host interference with replication
72
When are nonstructural proteins present?
only during replication inside host cell - WILL NEVER SEE OUTSIDE HOST CELL
73
What is an incomplete virion?
virion without nucleic acid only an empty capsid
74
Describe and defective virions?
cannot replicate, lacks full copy of viral genes due to mutations or errors
75
When does replication of defective virions occur?
mixed infections with a helper virus
76
What is a pseudovirion?
contains non-viral genome, usually host nucleic acid look like virus but DO NOT REPLICATE
77
What is a pseudotype?
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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