Viruses 1 - Structure Flashcards
(66 cards)
1
Q
Viruses are non-cellular - what does this mean?
A
- no nucleus
- no cytoplasm
- no organelles
2
Q
What are viruses?
A
- small parasite/particle/agents
3
Q
Viruses are obligate intracellular parasites - what does this mean?
A
- they cannot reproduce outside of the host cell
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
5
Q
What does a virion (entire particle) consist of?
A
- nucleic acids and protein capsule
6
Q
What can be used for classification of viruses?
A
- RNA or DNA - with genome structure
7
Q
What standard organelles do viruses lack?
A
- mitochondria
- chloroplasts
8
Q
What is differential diagnosis?
A
- possible conditions that share the same symptoms - could have many diagnoses
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
10
Q
What are examples of poxviridae?
A
- Bovine papular stomatitis virus - not in UK
- orf in sheep and goats
11
Q
What are examples of Herpesviridae?
A
- Aujeszkys disease in pigs - eradicated from UK but could return
- Bovine infectious rhinotracheitis (IBR) = common
12
Q
What’s in the normal cat vaccine?
A
- cat flu = feline herpes virus and feline calicivirus
- feline infectious enteritis
- feline leukaemia virus
13
Q
What are examples of Parvoviridae?
A
- parvovirus in dogs
- feline panleukopenia in cats
14
Q
What are examples of paramyxoviridae?
A
- Rinderpest = ruminants
- Newcastle disease = major poultry disease (vaccination)
- canine distemper in dogs (vaccination)
15
Q
What’s an example of coronaviridae?
A
- feline enteric coronavirus - feline infectious peritonitis (FIP) = fatal
16
Q
What is the size of most viruses and what do we need to see them?
A
- 20-250 nm
- require electron microscope
17
Q
What is the size of most bacteria and what do we require to see them?
A
- 5-10 um
- light microscope
18
Q
What is the size of a human erythrocyte and what do we require to see it?
A
- 8 um
- light microscope
19
Q
The genome contains either … or …
A
- DNA or RNA
20
Q
What viruses are double stranded?
A
- DNA viruses
21
Q
What viruses are single-stranded?
A
- RNA viruses
22
Q
DNA replication happens where?
A
- in the nucleus
23
Q
where does RNA replication happen?
A
- mostly in the cytoplasm
24
Q
Where are DNA genes found and what type of mutation?
A
- all genes on a single molecule (mostly small point mutation)
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
