Lecture 23 - Intro to virology Flashcards

(44 cards)

1
Q

why aren’t viruses living organisms?

A

because it cannot do anything outside a host cell
- can’t make many proteins by itself

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how do viruses replicate?

A

they use host mechanisms and are assembled, they do not replicate by division.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how are viruses filterable agents?

A

they are very small and can’t be filtered the way that bacteria can

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

true or false, viruses contain DNA and RNA genomes

A

false, their genomes may be DNA OR RNA, not both.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

describe general morphology of viruses

A

naked capsid or envelope morphology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

true or false, proteins not provided by the host must be made by the virus

A

False, viruses cannot make proteins, but instead carry the DNA or RNA required to make proteins not provided by the host cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

viral components assemble how?

A

the components must self-assemble

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe virus size

A

the largest viruses are about the size of the smallest bacterium we know of (chlamydia)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

is SARS-Cov2 an RNA virus or a DNA virus?

A

human RNA virus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

describe the components of the basic virus structure

A

Nucleic acid genome covered by a capsid, which is made of capsomers.
some (typically larger ones) have an envelope, which is a membrane layer of lipids and sometimes proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is a capsid/nucleocapsid

A

a protective protein coat for viral nucleic acids (DNA/RNA) that is formed by self assembly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how are the envelopes and envelope proteins on viruses made?

A

they are encoded by the virus but are made by the host
- aka spike proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe the 2 naked capsid morphologies

A

lots of capsomer subunits bind helical nucleic acids, or
proteins assemble into pentamer capsomeres, which form an icosahedron (20 sides)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the most common structure of naked viruses and why?

A

the icosahedral structure due to its protective and stable structure.
the helical structure is very uncommon in human viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the four virus morphologies?

A
  • helical naked capsid
  • polyhedral naked capsid
  • spherical (with envelope)
  • bacteriophage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are spike proteins used for?

A

very specific host attachment (narrow host cell spectrum)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

describe how narrow the spike proteins host cell spectrum is

A

enough to be specific to a type of cell within a certain type of host (e.g human T cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

describe binding of SARS-Cov2 to its specific host cell

A

spike protein binds to cells that carry the ACE2 receptor in airways

19
Q

true or false, SARS-Cov2 would not be infectious if it didn’t have its spike protein

20
Q

describe properties of the naked capsid

A

environmentally stable to:
- temp
- acid
- proteases
- detergents
- drying

21
Q

what are the consequences of naked capsid viruses

A
  • can be spread easily
  • can dry out. and still contain infectivity
  • can survive the adverse gut conditions
  • can be resistant to poor sewage treatment
22
Q

describe properties of the enveloped virus

A

environmentally labile and disrupted by:
- acid
- detergent
- drying
- heat

23
Q

what are the consequences of the enveloped virus?

A
  • must stay wet
  • cannot survive in gut
  • spreads in large droplets such as respiratory droplets, blood and breast milk
24
Q

why are envelopes viruses more sensitive to heat, detergent and drying out?

A

because they disrupt the membrane, and if that gets disrupted, then the virus is no longer infectious and probably no longer alive

25
describe virus replication
1:Virus recognizes and binds to specific host cell surface receptors. 2: Virus enters the cell via endocytosis or membrane fusion (enveloped viruses). 3: Viral capsid is removed, releasing the viral genome into the host cell. 4: Viral genome is replicated, transcribed, and translated using host machinery. 5: New viral components are spontaneously assembled into complete viruses 6: Viruses exit the cell by lysis (naked viruses) or budding from spike-protein containing membrane (enveloped viruses)
26
true or false, when naked viruses leave the cell they kill it, but when enveloped viruses leave the cell survives
most of the time yes, true - cell can regenerate the membrane, but if there are a lot of viruses being made then the cell may be overwhelmed
27
How do dsDNA viruses replicate and make proteins? What is the main enzyme used and its source?
use the host’s DNA-dependent RNA polymerase in the nucleus to transcribe mRNA and make proteins
28
How do ssDNA viruses replicate and synthesize proteins? What enzyme is required and where does it come from?
ssDNA viruses use host DNA polymerase to synthesize a complementary DNA strand, forming dsDNA. Then, host RNA polymerase transcribes mRNA.
29
How do positive polarity RNA viruses replicate and make proteins? What is the key enzyme and its origin?
+ssRNA acts as mRNA and is directly translated by host ribosomes to make viral RNA-dependent RNA polymerase. then this enzyme replicates the viral RNA, first making a –ssRNA template, which is then used to synthesize more +ssRNA genomes.
30
How do negative polarity RNA viruses replicate and make proteins? What is the key enzyme and its origin?
–ssRNA is used to transcribe +ssRNA using a viral RNA-dependent RNA polymerase, which is carried within the viral genome. Then +ssRNA is translated by host ribosomes
31
How do retroviruses replicate and make proteins? Include the nucleic acid type, key enzyme, and source
contain +ssRNA and use viral reverse transcriptase (from the viral genome) to make dsDNA, which integrates into the host genome
32
how do bacteriophages work?
they very specifically bind to a host bacteria and injects its genome into the cell, leaving the rest of the bacteriophage outside the cell
33
how do bacteriophages leave the host cell?
they assemble and can only exit via cell lysis
34
what are latent virus infections?
a persistent infection where the virus does not reproduce and so there are no clinical symptoms. - virus can occasionally activate and produce symptomsq
35
describe how herpes virus is a latent virus
they virus site latent in neurons, but can be activated due to stress, fever or UV light and causes cold sores
36
describe how chicken pox is a latent virus
sits latent but resurfaces when immune system weakens by disease or old age and causes shingles
37
describe how HIV is a latent virus
sits latent in T cells and macrophages and is integrated in the genome - leads to AIDS
38
describe oncogenic viruses
viruses that integrate into host genome close to proto-oncogens activation of the virus also activates the proto-oncogene and can cause cancer
39
what are the three common oncogenic viruses?
- Epstein-barr virus - Human papilloviruses: cervical cancer - Human Herpesvirus 8
40
what are viroids?
short naked fragments of ssRNA that infect plants
41
what are prions?
small infectious proteins that cause neurological disease
42
true or false, resistance is grown to antiviral drugs
true
43
at which stages can antiviral drugs inhibit viral activity?
at all stages each antiviral treatment is specific to inhibiting a step of the pathway
44
why are antiviral drugs so different to antibiotics?
because they inhibit viral reproduction, which is very different from bacterial reproduction