PRIS > Viruses 1 - Structure > Flashcards

Viruses 1 - Structure Flashcards

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1
Q

Viruses are non-cellular - what does this mean?

A
  • no nucleus
  • no cytoplasm
  • no organelles
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2
Q

What are viruses?

A
  • small parasite/particle/agents
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3
Q

Viruses are obligate intracellular parasites - what does this mean?

A
  • they cannot reproduce outside of the host cell
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4
Q

How do viruses produce proteins and nucleic acid to reproduce?

A
  • they are inert outside of host
  • so utilise host cell processes to produce proteins and nucleic acid to reproduce
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5
Q

What does a virion (entire particle) consist of?

A
  • nucleic acids and protein capsule
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6
Q

What can be used for classification of viruses?

A
  • RNA or DNA - with genome structure
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7
Q

What standard organelles do viruses lack?

A
  • mitochondria
  • chloroplasts
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8
Q

What is differential diagnosis?

A
  • possible conditions that share the same symptoms - could have many diagnoses
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9
Q

What are the different ways we can classify viruses?

A
  • nature of genome
  • presence of an envelope
  • morphology
  • genenome configuration
  • genome size
  • virion size
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10
Q

What are examples of poxviridae?

A
  • Bovine papular stomatitis virus - not in UK
  • orf in sheep and goats
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11
Q

What are examples of Herpesviridae?

A
  • Aujeszkys disease in pigs - eradicated from UK but could return
  • Bovine infectious rhinotracheitis (IBR) = common
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12
Q

What’s in the normal cat vaccine?

A
  • cat flu = feline herpes virus and feline calicivirus
  • feline infectious enteritis
  • feline leukaemia virus
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13
Q

What are examples of Parvoviridae?

A
  • parvovirus in dogs
  • feline panleukopenia in cats
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14
Q

What are examples of paramyxoviridae?

A
  • Rinderpest = ruminants
  • Newcastle disease = major poultry disease (vaccination)
  • canine distemper in dogs (vaccination)
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15
Q

What’s an example of coronaviridae?

A
  • feline enteric coronavirus - feline infectious peritonitis (FIP) = fatal
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16
Q

What is the size of most viruses and what do we need to see them?

A
  • 20-250 nm
  • require electron microscope
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17
Q

What is the size of most bacteria and what do we require to see them?

A
  • 5-10 um
  • light microscope
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18
Q

What is the size of a human erythrocyte and what do we require to see it?

A
  • 8 um
  • light microscope
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19
Q

The genome contains either … or …

A
  • DNA or RNA
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20
Q

What viruses are double stranded?

A
  • DNA viruses
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21
Q

What viruses are single-stranded?

A
  • RNA viruses
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22
Q

DNA replication happens where?

A
  • in the nucleus
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23
Q

where does RNA replication happen?

A
  • mostly in the cytoplasm
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24
Q

Where are DNA genes found and what type of mutation?

A
  • all genes on a single molecule (mostly small point mutation)
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25
Where are is RNA found and how does it allow for faster mutations?
- different molecules and segmented allows for faster mutations
26
Which has a higher mutation rate - DNA or RNA?
- RNA
27
Are DNA viruses stable or unstable? and by process of elimination what are RNA viruses?
- DNA viruses are stable - RNA viruses are unstable
28
Positive sense vs negative sense are to do with what?
- to do with ability to produce viral proteins directly or through intermediate stage
29
What is antigenic drift?
- where a virus is genetically diverse as a consequence of accumulating and tolerating point mutations
30
What is antigenic shift?
- Where a virus such as influenza can reassort their segmented genomes to generate novel viruses with altered host range and virulence
31
Why can RNA be immediately translated by the host cell?
- positive sense viral RNA is similar to mRNA so can immediately be translated by the host cell
32
Positive sense means ...
segmented
33
Negative sense means?
- non -segmented
34
What components make up an enveloped virion?
- matrix - membrane glycoprotein (peplomer) - capsid - lipid envelope - genetic material
35
What components make up a naked or non-enveloped virion?
- capsid - genetic material
36
What is a capsid?
- a protective layer surrounding the nucleic acid
37
What viruses can a capsid be found?
- in both enveloped and naked viruses
38
What is a capsid composed of?
- comprised of capsomeres - proteinaceous
39
The shape of the capsid is the characteristic of a virus - what 3 forms of symmetry?
- icosahedral - helical - complex
40
Describe a Icosahedral capsid
- composed of capsomeres - subunits of capsid - icosohedron - polyhedron with 20 faces - polyhedron = three dimensional shape with flat polygonal faces - straight edges and sharp corners - very structural - campsomere - repeated protein subunit - efficient and requires less coding as repetitive
41
What symmetry does a icosahedral have and what may it look like?
- 5-3-2 symmetry - may look spherical
42
An icosahedral capsid is very stable and non-enveloped which means ...
- it can survive months in the environment
43
What in a normal dog vaccine
- parvovirus - distemper - leptospirosis - infectious hepatitis - kennel cough
44
Describe a helical capsid
- structural unit = single type of protein arranged around central axis - forms helical structure
45
Is a helical capsid enveloped or non-enveloped?
- all enveloped
46
What does a helical capsid produce?
- produces rod-shaped or filamentous viruses
47
Describe a complex capsid?
- neither icosahedral or helical - very large viruses - animal viruses - only poxviridae
48
What is an envelope?
= lipid coating surrounding the virion
49
What does an envelop have for binding to receptor sites?
- glycoprotein spikes
50
How does an envelope affect a virus?
- affects how and where a virus replicates and therefore effects pathogenesis and host immune response
51
Name the components of a virus?
- lipid membrane (from the host) - Proteins spikes (glycoprotein)
52
What sugars are linked to an envelope?
- haemaglutinin (HA) - Neuraminidase (NA)
53
Name 4 enveloped viruses?
- Rhabdoviridae (e.g. Rabies) - Orthomyxoviridae (e.g. Influenza) - Paramyxoviridae (e.g. Canine distemper) - Coronaviridae (e.g. Coronavirus)
54
Name 2 non-enveloped viruses?
- Picornaviridae (e.g. FMD) - Parvoviridae (e.g.Parvovirus)
55
What are non-enveloped viruses?
- surface = protein - Stable in regard to: Temperature, pH, proteases, detergents, drying, released by lysis - resistant to detergents
56
What are enveloped virus?
- surface = lipids, proteins, glycoproteins - Labile in regard to: Acids, detergents, drying, heat. released by budding - easily destroys by detergents
57
So due to the structure of a non-enveloped virus what does this mean for its functions?
- easily spread - can dry out and retain infectivity - can survive adverse events in the gut - many lyse cell to exit
58
So due to the structure of a enveloped virus what does this mean for its functions?
- less easily spread - large droplets, secretions, infusions - must sat wet - less likely to survive in GIT - Do not need to destroy cell to be released
59
What are structural proteins?
- capsid or envelope proteins
60
What do non-enveloped capsid proteins do?
- Protect Genome - And deliver viral nucleic acid to cell to enable attachment
61
Enveloped glycoproteins are embedded in what layer?
- Embedded in lipid layer
62
Why are glycoproteins encoded and what are they encoded by?
- Glycoproteins are encoded by the virus for attachment
63
Hosts can develop antibodies against glycoproteins if what is present?
-
64
What is a non-structural protein?
- Not part of structure often enzymes
65
What is a non-structural protein produced in?
- Produced in host cell by virus following infection - virus manipulating host to own advantage
66
Why are non-structural proteins useful?
- Can be useful for identifying viruses - Helps differentiate infected from vaccinated animals
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