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PRIS > Viruses 1 - Structure > Flashcards

Viruses 1 - Structure Flashcards

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 why type of mutation?

A
  • all genes on a single molecule (mostly small point mutation)
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25
Q

Where are is RNA found and how does it allow for faster mutations?

A
  • different molecules and segmented allows for faster mutations
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26
Q

Which has a higher mutation rate - DNA or RNA?

A
  • RNA
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27
Q

Are DNA viruses stable or unstable?
and by process of elimination what are RNA viruses?

A
  • DNA viruses are stable
  • RNA viruses are unstable
28
Q

Positive sense vs negative sense to to do with what?

A
  • to do with ability to produce viral proteins directly or through intermediate stage
29
Q

What is antigenic drift?

A
  • where a virus is genetically diverse as a consequence of accumulating and tolerating point mutations
30
Q

What is antigenic shift?

A
  • Where a virus such as influenza can reassort their segmented genomes to generate novel viruses with altered host range and virulence
31
Q

Why can RNA be immediately translated by the host cell?

A
  • positive sense viral RNA is similar to mRNA so can immediately be translated by the host cell
32
Q

Positive sense means …

A

segmented

33
Q

Negative sense means?

A
  • non -segmented
34
Q

What does components make up an enveloped virion?

A
  • matrix
  • membrane glycoprotein (peplomer)
  • capsid
  • lipid envelope
  • genetic material
35
Q

What components make up a naked or non-enveloped virion?

A
  • capsid
  • genetic material
36
Q

What is a capsid?

A
  • a protective layer surrounding the nucleic acid
37
Q

Where is a capsid found?

A
  • in both enveloped and naked viruses
38
Q

What is a capsid composed of?

A
  • comprised of capsomeres - proteinaceous
39
Q

The shape of the capsid is the characteristic of a virus - what 3 forms of symmetry?

A
  • icosahedral
  • helical
  • complex
40
Q

Describe a Icosahedral capsid

A
  • 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
Q

What symmetry does a icosahedral have and what may it look like?

A
  • 5-3-2 symmetry
  • may look spherical
42
Q

An icosahedral capsid is very stable and non-enveloped which means …

A
  • it can survive months in the environment
43
Q

What in a normal dog vaccine

A
  • parvovirus
  • distemper
  • leptospirosis
  • infectious hepatitis
  • kennel cough
44
Q

Describe a helical capsid

A
  • structural unit = single type of protein arranged around central axis - forms helical structure
45
Q

Is a helical capsid enveloped or non-enveloped?

A
  • all enveloped
46
Q

What does a helical capsid produce?

A
  • produces rod-shaped or filamentous viruses
47
Q

Describe a complex capsid?

A
  • neither icosahedral or helical
  • very large viruses
  • animal viruses - only poxviridae
48
Q

What is an envelop?

A

= lipid coating surrounding the virion

49
Q

What does an envelop have for binding to receptor sites?

A
  • glycoprotein spikes
50
Q

How does an envelope affect a virus?

A
  • affects how and where a virus replicates and therefore effects pathogenesis and host immune response
51
Q

Name the components of a virus?

A
  • lipid membrane (from the host)
  • Proteins spikes (glycoprotein)
52
Q

What sugars are linked to an envelop?

A
  • haemaglutinin (HA)
  • Neuraminidase (NA)
53
Q

Name 4 enveloped viruses?

A
  • Rhabdoviridae (e.g. Rabies)
  • Orthomyxoviridae (e.g. Influenza)
  • Paramyxoviridae (e.g. Canine distemper)
  • Coronaviridae (e.g. Coronavirus)
54
Q

Name 2 non-enveloped viruses?

A
  • Picornaviridae (e.g. FMD)
  • Parvoviridae (e.g.Parvovirus)
55
Q

What are non-enveloped viruses?

A
  • surface = protein
  • Stable in regard to: Temperature, pH, proteases, detergents, drying, released by lysis
  • resistant to detergents
56
Q

What are enveloped virus?

A
  • surface = lipids, proteins, glycoproteins
  • Labile in regard to:
    Acids, detergents, drying, heat. released by budding
  • easily destroys by detergents
57
Q

So due to the structure of a non-enveloped virus what does this mean for its functions?

A
  • easily spread
  • can dry out and retain infectivity
  • can survive adverse events in the gut
  • many lyse cell to exit
58
Q

So due to the structure of a enveloped virus what does this mean for its functions?

A
  • 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
Q

What are structural proteins?

A
  • capsid or envelope proteins
60
Q

What do non-enveloped capsid proteins do?

A
  • Protect Genome
  • And deliver viral nucleic acid to cell to enable attachment
61
Q

Enveloped glycoproteins are embedded in what layer?

A
  • Embedded in lipid layer
62
Q

Why are glycoproteins encoded and what are they encoded by?

A
  • Glycoproteins are encoded by the virus for attachment
63
Q

Hosts can develop antibodies against glycoproteins if what is present?

A

-

64
Q

What is a non-structural protein?

A
  • Not part of structure often enzymes
65
Q

What is a non-structural protein produced in?

A
  • Produced in host cell by virus following infection
  • virus manipulating host to own advantage
66
Q

Why are non-structural proteins useful?

A
  • Can be useful for identifying viruses
  • Helps differentiate infected from vaccinated animals

PRIS (16 decks)

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