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BVetMed 1 > POS - Virology > Flashcards

POS - Virology Flashcards

1
Q

What is a virus?

A

An obligate intrcellular parasite

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2
Q

What does it need?

A

A host cell

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3
Q

What are the details?

A

Very small - need electron microscope to visualise

Lacks organelles - no nucleus, mitochondria or ribosomes

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4
Q

What is the structure of a naked/un enveloped virus?

A

Capsid surrounding viral nucleic acid and viral enzymes

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5
Q

What is the structure of an enveloped virus?

A

Lipid bilayer with viral envelop protein surrounds the capsid

This surrounds the viral nucleic acid and viral enzymes

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6
Q

What is the virus envelope made of?

A

Host derived lipid bilayer
Virus encoded glycoproteins, which form spikes and protrude from virus surface.

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7
Q

How do you classify a virus with its structure?

A

Genome structure and composition

Structure and symmetry of the capsid

Presence or absence of an envelope

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8
Q

How do you split viruses depending on their genome?

A

DNA - double stranded DNA virus or single stranded DNA virus with some circular.

RNA - double stranded RNA or single stranded RNA. This ssRNA then splits to positive - translated directly to proteins or negative - has to be translated to positive before translated to proteins.

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9
Q

Whats an example of ssDNA viruses?

A

Parvoviridae
Circoviridae

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10
Q

Whats an example of dsDNA viruses?

A

Poxviridae
Herpesviridae
Papillomaviridae
Adenoviridae
Papovaviridae

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11
Q

What are DNA viruses?

A

All monopartite (all viral genes on a single segment)

Mostly ds

Few circular

Little diversity

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12
Q

What are RNA viruses?

A

Mostly ss

All linear

Can have more than one segment

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13
Q

What are examples of dsRNA?

A

Reoviridae
Birnaviridae

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14
Q

What are examples of +ve ssRNA?

A

Coronaviridae
Picornaviridae
Arteriviridae
Flaviviridae

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15
Q

What are examples of -ve ssRNA?

A

Paramyxoviridae or Orthomyxoviridae

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16
Q

What enzyme do RNA viruses need to take with them?

A

RNA polymerase to copy the genome so are dependent

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17
Q

Why are RNA polymerases error prone and what are the consequences of this?

A

No proof reading and this makes the viruses more variable and able to evolve rapidly.

18
Q

Why are RNA viruses segmented?

A

To allow reassortment to increase diversity

eg. bluetongue and influenza

19
Q

How do RNA viruses reassort?

A

Mix genes during replication, requiring simultaneous infection of different strains

2 strains of different virus infect and due to reassortment there can be new progeny.

20
Q

What are the three types of capsid structure?

A

Icosahedral

Helical

Complex

21
Q

What is the icosagedral capsid look like?

A

Regular, strong and compact

12 vertices, with 20 triangular sides (5,3 and 2 symmetry)

Composed of capsomers

Most without envelop

22
Q

What is a capsomer?

A

The basic building block of a capsid made of repeating protein units.

Either penton or hexon.

23
Q

What is an example of a non-enveloped icosahedral virus?

A

Parvoviridae

12 capsomers, 60 copies 3 proteins VP2. Extremely stable

24
Q

What is a helical capsid?

A

A single capsid protein in a spiral configuration. All are enveloped.

25
Q

What is an example of an enveloped helical capsid virus?

A

Paramyxoviridae - ssRNA, spherical and much larger e.g. canine distemper

Rhabdoviridae - bullet shaped with spike like projections e.g. rabies

26
Q

What is a complex capsid?

A

Asymmetrical and neither helical or ocosahedral

27
Q

Whats an example of a complex capsid virus?

A

Pox viruses - large enveloped dsDNA, brick shaped or ovoid virion e.g. orf.

28
Q

What are naked viruses?

A

Icosahedral capsid e.g. adenovirus

29
Q

What are enveloped viruses?

A

Few icosahedral e.g. icosahedral
All helical are enveloped e.g helical
Mammalian complex are enveloped e.g. pox

30
Q

What are characteristics of enveloped viruses?

A

Pleomorphic ( not regular shape)
Has host derived lipid bilayer and embedded viral glycoproteins
Contain receptors needed for virus entry

31
Q

How do enveloped viruses aquire an envelope?

A

As they bud through the host membrane (except poxvirus)

32
Q

How are naked viruses released?

A

By lysis

33
Q

What are the biological properties of enveloped viruses?

A

More fragile so more easily destroyed by GIT, detergents, disinfectants and outside environment.

Needs to stay wet so not likely spread

Cause persistent infections (doesnt kill cell)

Needs receptors on the envelop to enter

34
Q

What are the biological properites of unenveloped viruses?

A

Environmentally stable to temp, drying out, pH, detergents and proteases.

Easily spread and can survive drying out.

Has to kill cell via lysis

35
Q

What are structural viral proteins?

A

Capsid proteins
Envelope proteins
Matrix protein (layer inside envelope and outside capsid)
Virion-associated enzyme

36
Q

What are non-structural proteins/

A

Often enzymes involved in replication cycle
Some regulatory proteins, oncoproteins etc.

37
Q

What is the function of virus capsid proteins?

A

Protect the viral nucleic acid
Capsids contain receptors that attach to host cell to allow entry

38
Q

What are the function of virus envelope proteins?

A

Often glycosylated, embedded proteins.
Contain preceptors to attach to a permissive host cell receptor
Targes of host immune response
Interact with capsid during virus assembly

39
Q

What are the function of viral matrix proteins?

A

Connects envelope with the virus capsid.
Crucial in interaction and assembly
Found in paramyxovirus, orthomyxoviruses, herpesvirus and retrovirus

40
Q

What is the function of enzymes that are structural proteins?

A

RNA viruses carrying own RNA polymerase as a structural protein

Seen in all -ve sense RNA viruses

41
Q

What is the function of non structural viral proteins?

A

Made in virus-infected cell, often enzymes involved in viral replication (proteases, helicases, polymerase and protein primers)

Help proteins avoid host immune response

Targets T cell epitopes.

BVetMed 1 (53 decks)

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