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Fundamentals of Microbiology > Virology > Flashcards

Virology Flashcards

1
Q

Define a virus

A

Infectious, obligate intracellular parasite comprising of genetic material surrounded by a protein coat

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2
Q

What do viruses use host cell machinery for

A

To replicate the viral genome and produce viral proteins

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3
Q

Viruses do not replicate by division - what do they do

A

Assemble from proteins and genomes formed from the host cell machinery

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4
Q

Describe what a virus is like outside of a host cell

A

Inert / Inactive

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5
Q

In host cells what do viruses turn the host cells into

A

Virus factories

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6
Q

What is a virion

A

Complete infectious viral particle

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7
Q

What is a capsid and what is its function

A

A protein coat - it protects the viral genetic material

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8
Q

What do capsids self assemble from

A

Multiple copies of structural proteins

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9
Q

Name given to an individual protein subunit of a capsid

A

Protomer

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10
Q

What makes up a nucleocapsid

A

Capsid + Viral nucleic acid

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11
Q

Describe a helical capsid

A

Hollow tubes with protein walls and the nucleic acid sits on the inside

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12
Q

Describe a Icosahedral capsid

A

20 triangular faces arranged around the surface of a sphere constructed of pentamers or hexamers

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13
Q

Name given to cells with and without an envelope

A

Enveloped and naked

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14
Q

What are viral envelopes made of and how are they accquired

A

Lipo-protein bilayer
When virus buds through host cell-plasma membrane

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15
Q

What is the function of spike proteins

A

Involved in viral attachment to host cell antigenic site / host’s cell receptors

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16
Q

If enzymes are present in viruses what is their function

A

Involved in replication of viral nucleic acids

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17
Q

The viral genome can go 1 of 2 ways in 5 senses - what are they

A

DNA or RNA
ds or ss
linear or circular
continuous or segmented
ss can be + or -

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18
Q

What does each segment code for in the viral genome

A

A protein

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19
Q

By convention what ss is +

A

mRNA

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20
Q

What has to happen to the viral genome to enable translation into proteins by host ribosomes

A

It needs to be converted to mRNA

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21
Q

6 stages of viral replication

A
  1. Attachment to host cell via specific receptor
  2. Entry into host cell
  3. Uncoating - liberation of viral genome from viral protein coat
  4. Synthesis of proteins and replication of viral genome
  5. Self-assembly of nucleocapsids
  6. Release from the cell host
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22
Q

How are steps 1 and 6 different for enveloped and non enveloped cells

A

Enveloped - Endocytosis or membrane fusion - budding
Non-enveloped - Endocytosis - lysis

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23
Q

The viral envelope is normally formed from the host’s PM but what else can it be made from

A

Golgi apparatus
ER

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24
Q

What are the 3 classification of viruses

A

DNA viruses
RNA viruses
Retro-transcribing viruses

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25
What has to happen to ssDNA before translation
Must be converted into dsDNA
26
What enzyme do RNA viruses use
RNA-dependent RNA polymerases (RdRp)
27
What 2 enzymes do retro transcribing viruses use
Reverse transcriptase (RT) Integrase
28
How are virus names written
Lower case and without italic
29
What are 2 techniques used to measure the number of infectious viral particles
Plaque assay End point dilution assay
30
What are 2 techniques used to measure the number of viral particles
Electron microscopy ELISA - viral proteins qPCR - viral genome
31
What does a plaque assay allow
Determination of the virus titre (concentration) in a sample
32
What are plaques
Circular zone of lysed (dead) cells
33
Why do you cover the cells in agar during a plaque assay
To restrict diffusion of virus particles
34
What does end-point dilution assay allow
Determination of the dilution of a virus required to infect 50% of inoculated cell cultures
35
During the 1 step growth cycle how do you ensure that infection is synchronous
Short exposure to a high number of virions
36
What can the 1 step growth cycle be used to analyse
Virus and host factors that facilitate viral replication
37
What are the 3 periods in the 1 step growth cycle
Eclipse - no infectious viral particles Burst - huge amplification in short amount of time Plateau - no production of infectious viral particles
38
6 routes of infection in humans (3 tracts)
Eye - conjunctiva Respiratory tract Gastrointestinal tract Urogenital tract Skin - must be breached Placenta in pregnant woman
39
4 main routes of infection - ACVV
Airborne, contact, vehicle and vector
40
What is horizontal and vertical transfer of disease
H - person to person V - mother to unborn child
41
What is a viral pantropism
Where a virus can infect all tissues
42
Why does apoptosis stop viral replication
Viruses cannot replicate in a dead cell
43
What does a cell performing apoptosis form
Blebs
44
What is autophagy - what is formed and what is it discarded by
Cytoplasmic content is degraded by a formation of a membrane - autophagosome and phagocytosed by a lysosome
45
Cells must be accessible, susceptible and permissive for successful initiation of infection - what do these mean
Accessible - no protection from physical barrier Susceptible - appropriate receptor on surface Permissive - contain correct molecules for viral replication
46
What defences need to be overcome for initiation of infection
Antiviral defences
47
What are the 4 routes can viral diseases take when acute
Death Clearance and recovery Chronic then death Chronic then latent (replication can be replicated)
48
Where does replication occur after successful infection (2)
Site of entry or primary site
49
Name for when a virus is in the blood
Viremia
50
When is a virus considered a systemic spread
When is reaches the secondary site
51
Word for when viral infection leads to uncontrolled replication
Oncogenesis
52
Non-cell death effect of viruses on cells
Interference with normal cellular functions
53
Give an example of these defences Anatomical and chemical Intrinsic Innate Acquired
A+C - skin and mucus I - Apoptosis and autophagy I - Cytokinesis A - T and B lymphocytes
54
2 defence strategies cells use
Neutralising viral particles Prevention of intracellular replication
55
2 examples of indirect defence strategies
Apoptosis and autophagy
56
What are PRRs and what do they recognise
Pattern recognition receptors - viral nucleic acids
57
PRRs activate transcription factors that transcript what 2 things
IFN - interference Inflammatory cytokines
58
What do inflammatory cytokines lead to the secretion of
sentinel cells
59
2 examples of sentinel cells - what are their general role
Dendritic cells and natural killer cells Patrol tissues looking for signs of change
60
Give 2 ways dendritic cells are activated - where do they go
Viral proteins released from infected cells Apoptotic bodies Lymph nodes
61
What do dendrites bridge in the immune response
Innate to adaptive response
62
When type 1 interferons are secreted what receptors do they bind to and where are they found
Type 1 IFN receptors on infected cells or neighbouring cells
63
When Type 1 IFNs bind to the receptors this triggers a signalling cascade which leads to the expression of what and what effect does this gene have
Interferon stimulated gene Anti-viral effect
64
Give 2 examples of adaptive responses to viruses
Cytotoxic T lymphocytes Neutralising antibodies
65
What is reduced on the cell surface of infected cells that CTLs can recognise
MHC-1
66
Why are regulators of IFN and cytokines necessary
To avoid pathology
67
What are symptoms of a viral disease a consequence of
Host response to infection
68
2 reasons for immunopathology
Uncontrolled innate immune response Damaging effects of adaptive immune response

Fundamentals of Microbiology (16 decks)

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