3. Structure and Composition

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Pleomorphism

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Lecture 2

111 Terms

1

Pleomorphism

A virus’ ability to alter its shape or size

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400nm

Diameter of the largest viruses

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3

17nm

Diameter of the smallest viruses

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4

Capsid

Protein shell of a virus. Encases viral nucleic acid/genome. Composed of basic subunit proteins called capsomeres.

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5

Capsomeres

Capsids are composed of _________ held together by non-covalent bonds.

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Non-covalent

Capsids are composed of capsomeres held together by ___________ bonds.

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nucleocapsid

Capsid + Viral Nucleic Acid/Genome =

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Helical

Type of symmetry in which capsomeres and nucleic acid are wound together to form a spiral tube.

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9

True

TRUE/FALSE: In all animal viruses, the helical nucleocapsid is enclosed within a lipoprotein envelope.

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False

TRUE/FALSE: In all plant viruses, the helical nucleocapsid is enclosed within a lipoprotein envelope.

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11

Cannot

Due to interactions between nucleic acid and capsid proteins, incomplete virions - empty helical particles - (CAN/CANNOT) form.

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12

Icosahedral

Type of symmetry present in spherical viruses.

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13

Cubic

Icosahedral symmetry is also called __________ symmetry.

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14

Pentons, vertices

Icosahedral capsids are composed of ________ (pentagonal capsomeres) at the ___________, and hexons (hexagonal capsomeres) for the facets.

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Hexons, facets

Icosahedral capsids are composed of pentons (pentagonal capsomeres) at the vertices, and ________ (hexagonal capsomeres) for the _______.

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12, 20, 30

An icosahedron has (#) corners/vertices, (#) facets (triangular faces), and (#) edges.

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17

12

There are always (#) pentons in a spherical virus.

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18

True

(TRUE/FALSE): The number of hexons varies between spherical viruses.

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False

(TRUE/FALSE): The number of pentons varies between spherical viruses.

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20

pentagons

The T-number describes the relation between the number of __________________ and hexagons of the icosahedron.

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21

hexagons

The T-number describes the relation between the number of pentagons and _____________ of the icosahedron.

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22

triangulation

The “T” in “T-number” stands for

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23

H

The formula for the triangulation (T) -number is

T = __^(2) + h * k + k^(2)

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24

h

The formula for the triangulation (T) -number is

T = h^(2) + __ * k + k^(2)

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k

The formula for the triangulation (T) -number is

T = h^(2) + h * __ + k^(2)

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k

The formula for the triangulation (T) -number is

T = h^(2) + h * k + __^(2)

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27

distances

In the formula for T-number, h and k are the _____________ between successive pentagons on the virus surface per axis.

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28

simple

Parvovirus has a T value of 1. It is the most (SIMPLE/COMPLEX) icosahedron.

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reoviridae

______________ has two capsids with different T-numbers.

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family

*REVIEW: The name “Reoviridae” describes a(n): (ORDER/FAMILY/SUBFAMILY/GENUS/SPECIES).

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31

genus

*REVIEW: The name “Parvovirus” describes a(n): (ORDER/FAMILY/SUBFAMILY/GENUS/SPECIES).

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1

The parvovirus T-number is =

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33

2

The outer capsid of Reoviridae has a T=13 icosahedral symmetry, while the inner has a T=___.

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13

The outer capsid of Reoviridae has a T=____ icosahedral symmetry, while the inner has a T=2.

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reoviridae

The outer capsid of ______________ has a T=13 icosahedral symmetry, while the inner has a T=2.

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complex

Virions are composed of several parts with separate shapes and symmetries. This includes Pox viruses and bacteriophages. They have _____________ symmetry.

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37

symmetry

The viral capsid is responsible for the structural ___________ of the virus particle.

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38

nucleic acid

The viral capsid encases and protects the viral _________ ________ from enzymes, chemicals, and physical conditions.

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39

attachment

The receptor attachment proteins on a viral capsid facilitate the ______________ of the virus to specific receptors on susceptible host cells.

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40

receptors

The receptor attachment proteins on a viral capsid facilitate the attachment of the virus to specific _________ on susceptible host cells.

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host cells

The receptor attachment proteins on a viral capsid facilitate the attachment of the virus to specific receptors on susceptible __________ ___________.

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42

cell membranes

The viral capsid aids in interaction with the host ___________ ___________ to form the envelope.

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43

uncoating

The viral capsid aids in _______________ of the genome in the host cell.

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44

viral genome

The viral capsid aids in transport of the __________ __________ to the appropriate site.

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packaging

The viral capsid facilitates specific recognition and ____________ of the nucleic acid genome.

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antigenicity

The viral capsid can contribute to the ____________ of the virus, being targeted by and binding to antibodies.

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47

lipid bilayer

Virus envelopes are usually a _____________ _____________ with embedded proteins.

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48

proteins

Virus envelopes are usually a lipid bilayer with embedded ________________.

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49

budding

The process by which a virus acquires an envelope.

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50

matrix protein

There are two kinds of viral proteins typically found in an envelope: glycoprotein and __________ _____________.

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51

glycoprotein

There are two kinds of viral proteins typically found in an envelope: ____________ and matrix protein

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52

external glycoproteins

Virus envelope glycoproteins may be either ____________ ______________, anchored into the envelope, or channel proteins, hydrophobic proteins altering the permeability of the membrane.

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channel proteins

Virus envelope glycoproteins may be either external glycoproteins (anchored into the envelope) or ___________ ____________ (hydrophobic proteins altering the permeability of the membrane).

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antigens

External glycoproteins are typically major _____________ of the virus. They also contribute to hemagglutination, receptor binding, and membrane fusion.

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internal environment

Channel proteins alter the permeability of the viral membrane, helping to modify the ___________ ____________ of the virus.

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virus envelope matrix

__________ _________ _______ Proteins link the internal nucleocapsid to the lipid membrane envelope.

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assembly

Virus envelope matrix proteins play a crucial role in virus ____________

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nucleocapsid

The virus envelope matrix protein serves as the recognition site of ________________ at the plasma membrane.

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encapsidation

The virus envelope matrix protein mediates the ___________________ of the RNA-nucleoprotein cores into the membrane envelope.

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cytoplasmic membrane

The virus matrix protein coats the inside of the host cell’s ____________ ______________.

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host

The viral envelope is acquired from a cellular membrane of a ___________ cell.

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lipid envelope

The viral _________ ________ is maintained only in aqueous or moist environments.

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63

less

Enveloped viruses are (MORE/LESS) hardy than non-enveloped viruses.

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64

more

Enveloped viruses are (MORE/LESS) susceptible to sterilization than non-enveloped viruses.

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65

inactivated

Enveloped viruses can be ___________ by the dissolution of the lipid membrane with lipid solvents such as ether, chloroform, and detergents.

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cannot

Enveloped viruses (CAN/CANNOT) survive long periods in the environment.

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67

capsule

Which of the following is NOT a component of a virus

  • nucleic acid

  • capsid

  • envelope

  • capsule

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68

false

(TRUE/FALSE) The viral matrix protein is located between the viral nucleic acid and the capsid.

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69

true

(TRUE/FALSE): The viral matrix protein is located along the inside of the host cytoplasmic membrane

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70

DNA

Virus Nucleic Acids are typically either _____ or RNA.

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71

RNA

Virus nucleic acids are typically either DNA or ______.

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72

single

Viral nucleic acids - DNA/RNA - can be either double or ______ stranded.

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73

double

Viral nucleic acids - DNA/RNA - can be either single or __________ stranded.

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74

circular

Viral DNA can be linear or

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75

linear

Viral DNA can be either circular or

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sense

Viral RNA can be either (+) or (-)-_______________

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77

infectious

A (+)-sense RNA virus is a/n (INFECTIOUS/NONINFECTIOUS) genome.

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noninfectious

A (-)-sense RNA virus is a/n (INFECTIOUS/NONINFECTIOUS) genome.

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79

translated

The positive-sense RNA virus is similar to mRNA and can be immediately ___________ by the cell.

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80

converted

Negative-sense viral RNA is complementary to mRNA and must be ____________

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81

drift

Viruses can undergo antigenic _______ or antigenic shift

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shift

Viruses can undergo antigenic drift or antigenic _______

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83

antigenic drift

Mechanism of viral genetic diversity resulting in mutations.

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84

antigenic shift

Mechanism of viral genetic diversity resulting in recombination and reassortment

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85

Missense

Point mutations can be

  • silent

  • nonsense

  • __________

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86

nonsense

Point mutations can be

  • silent

  • ___________

  • missense

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87

silent

Point mutations can be

  • ____________

  • nonsense

  • missense

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88

recombination

The exchange of nucleotide sequences between different, but usually closely related, viruses during replication.

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89

reassortment

The most important mechanism for genetic diversity in viruses with segmented genomes

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true

(TRUE/FALSE) Recombination can occur with a virus that has a non-segmented genome.

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91

false

(TRUE/FALSE) Reassortment can occur with a virus that has a non-segmented genome.

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92

larger

DNA viruses are generally (LARGER/SMALLER) than RNA viruses.

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93

gene segment

Recombination occurs in a single ________ ________

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94

proteins

Enzymes and inhibitors are examples of viral ____________.

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95

enzymes

Retroviral integrase, reverse transcriptase, and nucleic acid polymerases are important viral _____________

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96

retroviral integrase

Enzyme produced by a retrovirus that enables it to integrate its genetic material into the DNA of the infected cell.

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97

reverse transcriptase

Enzyme used to generate complementary DNA from an RNA template.

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98

nucleic acid polymerase

Enzyme required for viral genome replication.

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99

viral nonstructural proteins

Proteins that play roles within the infected cell during virus replication or act in the regulation of virus replication or assembly. They are encoded by a viral genome and produced in the infected cell, but not packaged into the virus particles.

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100

false

(TRUE/VALSE) Nonstructural proteins are seen in extracellular virions.

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