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Fundamentals of Microbiology > Virology > Flashcards

Virology Flashcards

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Biology 101 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
Q

What has to happen to ssDNA before translation

A

Must be converted into dsDNA

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26
Q

What enzyme do RNA viruses use

A

RNA-dependent RNA polymerases (RdRp)

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27
Q

What 2 enzymes do retro transcribing viruses use

A

Reverse transcriptase (RT)
Integrase

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28
Q

How are virus names written

A

Lower case and without italic

29
Q

What are 2 techniques used to measure the number of infectious viral particles

A

Plaque assay
End point dilution assay

30
Q

What are 2 techniques used to measure the number of viral particles

A

Electron microscopy
ELISA - viral proteins
qPCR - viral genome

31
Q

What does a plaque assay allow

A

Determination of the virus titre (concentration) in a sample

32
Q

What are plaques

A

Circular zone of lysed (dead) cells

33
Q

Why do you cover the cells in agar during a plaque assay

A

To restrict diffusion of virus particles

34
Q

What does end-point dilution assay allow

A

Determination of the dilution of a virus required to infect 50% of inoculated cell cultures

35
Q

During the 1 step growth cycle how do you ensure that infection is synchronous

A

Short exposure to a high number of virions

36
Q

What can the 1 step growth cycle be used to analyse

A

Virus and host factors that facilitate viral replication

37
Q

What are the 3 periods in the 1 step growth cycle

A

Eclipse - no infectious viral particles
Burst - huge amplification in short amount of time
Plateau - no production of infectious viral particles

38
Q

6 routes of infection in humans (3 tracts)

A

Eye - conjunctiva
Respiratory tract
Gastrointestinal tract
Urogenital tract
Skin - must be breached
Placenta in pregnant woman

39
Q

4 main routes of infection - ACVV

A

Airborne, contact, vehicle and vector

40
Q

What is horizontal and vertical transfer of disease

A

H - person to person
V - mother to unborn child

41
Q

What is a viral pantropism

A

Where a virus can infect all tissues

42
Q

Why does apoptosis stop viral replication

A

Viruses cannot replicate in a dead cell

43
Q

What does a cell performing apoptosis form

A

Blebs

44
Q

What is autophagy - what is formed and what is it discarded by

A

Cytoplasmic content is degraded by a formation of a membrane - autophagosome and phagocytosed by a lysosome

45
Q

Cells must be accessible, susceptible and permissive for successful initiation of infection - what do these mean

A

Accessible - no protection from physical barrier
Susceptible - appropriate receptor on surface
Permissive - contain correct molecules for viral replication

46
Q

What defences need to be overcome for initiation of infection

A

Antiviral defences

47
Q

What are the 4 routes can viral diseases take when acute

A

Death
Clearance and recovery
Chronic then death
Chronic then latent (replication can be replicated)

48
Q

Where does replication occur after successful infection (2)

A

Site of entry or primary site

49
Q

Name for when a virus is in the blood

A

Viremia

50
Q

When is a virus considered a systemic spread

A

When is reaches the secondary site

51
Q

Word for when viral infection leads to uncontrolled replication

A

Oncogenesis

52
Q

Non-cell death effect of viruses on cells

A

Interference with normal cellular functions

53
Q

Give an example of these defences
Anatomical and chemical
Intrinsic
Innate
Acquired

A

A+C - skin and mucus
I - Apoptosis and autophagy
I - Cytokinesis
A - T and B lymphocytes

54
Q

2 defence strategies cells use

A

Neutralising viral particles
Prevention of intracellular replication

55
Q

2 examples of indirect defence strategies

A

Apoptosis and autophagy

56
Q

What are PRRs and what do they recognise

A

Pattern recognition receptors - viral nucleic acids

57
Q

PRRs activate transcription factors that transcript what 2 things

A

IFN - interference
Inflammatory cytokines

58
Q

What do inflammatory cytokines lead to the secretion of

A

sentinel cells

59
Q

2 examples of sentinel cells - what are their general role

A

Dendritic cells and natural killer cells
Patrol tissues looking for signs of change

60
Q

Give 2 ways dendritic cells are activated - where do they go

A

Viral proteins released from infected cells
Apoptotic bodies
Lymph nodes

61
Q

What do dendrites bridge in the immune response

A

Innate to adaptive response

62
Q

When type 1 interferons are secreted what receptors do they bind to and where are they found

A

Type 1 IFN receptors on infected cells or neighbouring cells

63
Q

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

A

Interferon stimulated gene
Anti-viral effect

64
Q

Give 2 examples of adaptive responses to viruses

A

Cytotoxic T lymphocytes
Neutralising antibodies

65
Q

What is reduced on the cell surface of infected cells that CTLs can recognise

A

MHC-1

66
Q

Why are regulators of IFN and cytokines necessary

A

To avoid pathology

67
Q

What are symptoms of a viral disease a consequence of

A

Host response to infection

68
Q

2 reasons for immunopathology

A

Uncontrolled innate immune response
Damaging effects of adaptive immune response

Fundamentals of Microbiology (16 decks)

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