Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Week 6 > viruses > Flashcards

viruses Flashcards

1
Q

what are viruses

A

simple acellular infection pathogens

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

what are viruses incapable of (compared to bacteria)

A

self-replication
- host
metabolic activity

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

what can viruses infect

A

every category of life

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

how big are viruses

A

20-200nm
- viruses that infect humans
too small for light microscopes

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

how is gene information stored in viruses

A

either RNA or DNA
either linear or circular
RNA - +ve sense (mRNA) or -ve sense (convert to +ve first)

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

what is the nucleocapsid

A

genome + capsid
- may also contain essential or accessory enzyme to facilitate initial replication
naked/ envlopes

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

what is a virion

A

fully assembled infection extracellular particle

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

what is the capsid comprised of

A

capsomeres
- several different polypeptides grouped together

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

what shapes can the capsid be

A

distinctive symmetry
helical/ icosahedral

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

give an example of an icosahedral virus

A

Hep B

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

what characterises an enveloped virus

A

phospholipid bilayer
- derived from the host cell
Golgi apparatus
ER
nuclear membrane

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

what is the envelope of an enveloped virus comprised of

A

lipids, virus proteins and glycoproteins

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

what are the host cell membrane proteins replaced by in viruses

A

virally encoded glycoproteins
- spike proteins

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

what are the spike proteins on influenzas called

A

Hemagglutinin and Neuraminidase

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

where are viral attachment proteins found

A

alongside capsid in naked viruses
anchored in the phospholipid bilayer of enveloped viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is viral tropism

A

ability of a given virus to productively infect a
particular cell - cellular tropism
tissue - tissue tropism
host species - host tropism

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

what are the modes of transmission for a virus

A

oral transmission
droplet transmission
direct inoculation
sexual transmission
trans-placental
direct skin contact

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

how are orally transmitted viruses spread

A

contaminated food + drink; saliva

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

give an example of an orally transmitted virues

A

Hep A/ norovirus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how are droplet transmitted viruses spread

A

inhalation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

give an example of a droplet transmitted virus

A

influenza
coronavirus
measles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how do directly inoculated viruses spread

A

injections; trauma; insect bites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

give an example of directly inoculated virus

A

yellow fever/ zika

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

give an example of a sexually transmitted virus

A

HIV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

give an example of a virus spread by skin-skin contact

A

herpes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

give an example of a single stranded +ve sense virus

A

ebola

27
Q

what symptoms characterise a common cold

A

blocked or running nose, coughing and sneezing, headaches, sore throat

28
Q

what symptoms characterise bronchoilitis

A

starts similarly to a cold but progresses to coughing/ wheezing/ difficulty breathing

29
Q

what symptoms characterise croup

A

harsh brassy/ barking cough

30
Q

give examples of respiratory illnesses

A

common cold, bronchiolitis, croup

31
Q

give 3 examples of coronaviruses

A

SARs-CoV
MERS-CoV
SARS-CoV-2

32
Q

what is a zoonose

A

a virus coming from an animal

33
Q

list the types of influenza

A

A B C D

34
Q

what types of influenza affects humans

A

A B

35
Q

what are the symptoms of human influenza

A

fever, chills, headache, muscle pain, extreme fatigue, dry cough, sore throat, blocked nose

36
Q

give three examples of human herpesviruses

A

measles
mumps
rubella

37
Q

what type of virus is HIV

A

single stranded +ve sense RNA retrovirus

38
Q

what CD4 count constitutes AIDS

A

220 cells/ mm3

39
Q

list some common opportunistic infections

A

Epstein-Barr virus
Fungal infections - oral candidiasis, Pneumocystis pneumonia
HHV-8 virus (Kaposi’s sarcoma)
cytomegalovirus (CMV) retinitis
cryptosporidium

40
Q

give two ways that viruses enter a host cell

A

macropinocytosis, membrane fusion

41
Q

describe micropinocytosis

A

taches to the host cell it can become engulfed by the host cell membrane

42
Q

describe membrane fusion

A

virus inserts itself into the host cell

43
Q

what are the stages of viral replication

A

attachment
penetration
uncoating
replication
assembly
virion release - lysis/ budding

44
Q

describe the attachment phase of viral replication

A

viral proteins on the capsid or phospholipid envelope interact with specific receptors on the host cellular surface
- specificity determines the host range (tropism) of a virus

45
Q

describe the penetration stage of viral replication

A

the process of attachment to a specific receptor can induce conformational changes in viral capsid proteins (/ lipid envelope)
- results in the fusion of viral + CMs
some DNA viruses can also enter the host cell through receptor-mediated endocytosis

46
Q

describe the uncoating stage of viral replication

A

the viral capsid is removed and degraded by viral enzymes or host enzymes, releasing the viral genomic nucleic acid

47
Q

describe the replication stage of viral replication

A

after the viral genome has been uncoated, transcription or translation of the viral genome is initiated
- this stage differs greatly between DNA and RNA viruses + viruses with opposite polarity
- culminates in the de novo synthesis of viral proteins and genome

48
Q

describe the assemebly stage of viral replication

A

after de novo synthesis of viral genome and proteins, which can be post-transcriptionally modified, viral proteins are packaged with newly replicated viral genome into new virions that are ready for release from the host cell
- also called maturation

49
Q

describe the lysis approach to the virion release stage of viral replication

A

results in the death of an infected host cell
viruses that cause this are referred to as cytotoxic

50
Q

give an example of a virus that uses lysis

A

variola major (smallpox)

51
Q

describe the budding approach to the virion release stage in viral replication

A

typically enveloped viruses (e.g. influenza A)
acquisition of the viral phospholipid envelope
viruses that cause this are referred to as cytopathic

52
Q

describe what can happen after virion release

A

some viral proteins remain within the host’s cell membrane
- acts as a potential target for circulating antibodies
- residual viral proteins that remain within the cytoplasms of a host cell can be processed and presented at CSM on MHC I

53
Q

describe the RNA replication of dsRNA viruses

A

one strand is transcribed by viral polymerase into mRNA

54
Q

describe the RNA replication of +ve sese ssRNA viruses

A

can be used directly as mRNA

55
Q

describe the RNA replication of -ve sense ssRNA viruses

A

viral polymerase converts into +ve sense mRNA strand, which can then be used as mRNA

56
Q

describe the RNA replication of retroviruses

A

-ve sense ssRNA -> -ve sense ssDNA (viral transcriptase enzyme) -> dsDNA -> enters nucleus -> integrated into host genome -> mRNA (host polymerase)

57
Q

describe HIV replication

A

1- Nucleocapsids containing viral genome and enzymes enters the target cell
2- Viral reverse transcriptase catalyses reverse transcription of ssRNA to form RNA-DNA hybrids
3- To yield HIV dsDNA the viral RNA template is partially degraded by ribonuclease H and the second DNA strand is synthesized
4- Viral dsDNA is translocated into nucleus and integrated into the host genome by the viral integrase enzyme
5- Transcription factors transcribe the proviral DNA into genomic ssRNA
6- Which is exported to cytoplasm
7- In cytoplasm, host-cell ribosomes catalyse synthesis of virus precursor proteins
8- Which are cleaved into viral proteins by viral proteases
9- HIV ssRNA and proteins assemble beneath the host-cell plasma membrane
10- Forming virion buds from it
11- Maturation occurs either in the forming buds or after budding from the host cell
During maturation, HIV proteases cleave the polyproteins into individual functions HIV proteins

58
Q

what 3 mechanisms cause viral genome variation

A

mutation
recombination
gene switching/ reassortment

59
Q

do RNA or DNA viruses mutate faster

A

RNA

60
Q

do ss or ds mutate faster

A

ss

61
Q

what is antigenic drift

A

small mutations within antigenic genes that allow viruses to to evade host immune systems

62
Q

describe gene recombination/ reassortment

A

2 strains of a virus infect the same host
recombination -> exchange of entire genes between two strands
reassortment -> exchange of entire segments of a genome between strains
- both result in antigenic shift

63
Q

how does influenza A exhibit antigenic drift / shift

A

8 segments of -ve sense ssRNA
- susceptible to insertion, deletion and substidution (drift)
able to co-infect multiple species (with B) (shift)
zoonotic spread of new chains

Week 6 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions