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Microbiology Block 1 > Virology > Flashcards

Flashcards in Virology Deck (66):
1

what is a virus?

obligate intracellular pathogens

2

can viruses replicate anywhere? Why?

no, they must replicate inside a host living cells, by using the host's cellular machinery to do transcription, translation and replication 

3

what do viruses synthesize?

virions

4

what do virions do?

they help in the transfer of  the viral genome (RNA or DNA) to other living cells

5

what do viruses lack?

mitochondria, ribosomes, enzymes

6

true or false: viruses are bigger than bacteria and host cells

false, they are much more smaller

7

what are the 2 stages of a virus?

1) Virion = the infectious form

2) intracellular form (its genome alone) = non-infectious 

8

what is the structural parts of a virus (after infection)?

which of these parts is optional?

1) Viral DNA/RNA

2) nucleocapsid

3) matrix tegument

4) envelope

 

the ENVELOPE is optional

9

what are the 3 forms that the nucleocapsid can have?

1) icosahedral

2) helical

3) complex

10

how do we find the viral envelope? (how does it look or what is it?)

its the host cell lipid bilayer, with viral glycolipids in the surface

11

how do you know if the virus is enveloped or naked?

enveloped = nucleocapsid + glycoproteins and the nuclear membrane 

naked = only the nucleocapsid

12

what makes up the nucleocapsid?

1) DNA/RNA

2) structural protein

13

what determines what steps and enzymes are necessary to create the viral mRNA?

the type of nucleic acid

14

what enzyme is important for single stranded RNA retrovirus?

reverese transcription

15

why is it very important to know what type of nucleic acid a virus is?

because by determining what type of nucleic acid the virus is, we can select the corret anti-biotic to treat it with

16

what type of nucleocapsid do all naked virus have?

icosahedral

17

what type of nucleocapsid do all enveloped viruses have?

complex

18

what is the function of the outer structural proteins?

1) protect the genetic material

2) mediates the attachment of the virus to specific host cell receptors on the cell surface

3) activate the immune system to kill virus cell (activate neutralizing antibodies and CTL's)

 

19

when does a immune response occur? (after what 2 events?)

1) natural exposure

2) immunization

20

what determines the viral classification?

nucleic acid and the envelope

21

what viruses are less stable?

enveloped DNA/RNA viruses

22

how are enveloped DNA/RNA viruses transmitted?

 through direct contact 

(blood or bodily fluids)

23

what viruses are more stable and can survive a long time in the environment?

naked DNA/RNA viruses

24

how do naked viruses spread?

through indirect means (fecal-oral route)

25

what is an example of an enveloped DNA virus?

Hep. B

26

what is an example of a naked RNA virus?

Hep A

27

What are the DNA viruses?

1) Parvovirus

2) Papillomaviridae

3) Polyomaviridae

4) Adenovirus

5) Herpes virus

6) Hepadnavirus

7) Poxvirus

28

what 2 viruses have polymerase?

1) Hepadnavirus

2) Poxvirus

29

All DNA viruses are icosahedral, except for?

Poxvirus

30

all DNA viruses are what single straded or double stranded?

Who is the exception?

double stranded DNA

Parvovirus

31

what is a double stranded RNA virus example?

Reovirus

32

what are the positive RNA viruses?

1) Calicivirus

2) Picorna

3) Flavivirus

4) Togavirus

5) Coronavirus

6) Retrovirus

33

what is an example of a retrovirus?

HIV

34

what are the 6 types of negative RNA viruses?

1) Paramyxovirus

2) Rhabdovirus

3) Filovirus

4) Orthomyxovirus

5) Bunyavirus

6) Arenavirus

35

what are the 5 steps of the viral cycle?

1) attachment

2) penetration

3) synthesys

4) assembly 

5) release

36

what is PFU?

is a plaque forming unit

once virus infects a single cell, spread and kill surrounding cells to cause a plaque (a clear area or dead cells) surrounded by live cells.

37

What is it called the time after the nucleic acid is released and before the virus starts replicating?

eclipse phase

38

the time before full virions are released after infection is called?

the latent phase

39

what do virions have that allows them to restrict the host cell specificity (or tropism)?

VAP ( virion attachment protein)

40

what are the VAP of the HIV virus? to what do they attach to?

GP 120---binds to CCR5 on macrophages

 

GP140 ----binds to CD4

41

what cells does HIV infect?

CD4 cells

42

what are the VAP of epstein-Bar virus? to what receptor do they bind? and on what cell?

CR2 and CD21

they bind to C3d complement receptor on B cells

43

to what does rhinovirus VAP bind to ? on what cells?

ICAM-1 on endothelial cells

 

44

what is the VAP of Influenza A virus? to what cells does it bind to?

sialic acid and binds to epithelial cells

45

where does penetration of a virus occur?

at the cell surface

46

where does uncoating occur in a virus?

once inside the cell

47

the process of uncoating is dependant on what?

it is pH dependant

48

in order for the virus to replicate, what must physically separate in the viral structure?

the capsid from the viral genome

49

uncoating depends on what in the host cell?

depends on cellular enzymes

50

if the virus loses this from its structure during uncoating  will lead to loss of ability to infect other cells...

structural proteins

51

what mechanisms are used to facilitate nucleic acid release?

1) clathrin-dependent pathway

2) macropinocytosis

3) caveolar pathway

4) clathrin- and cavolin-independant pathway

5) phagocytosis

52

the virion genome will encode this two types of genes:

early gene

late gene

53

what is the early gene made by the viral genome used for?

it is needed for replication

54

what is the late gene made from the viral genome used for?

it is required for packaging

55

what kind of proteins does the viral genome instruct the cell to produce?

structural and non-structural proteins

56

what are structural proteins?

are the late proteins found in virion particles

57

what are non-structural proteins?

early proteins produced in infected cells but not found in virions

58

what does the herpes virus have to do before it can integrate into the host genome?

it has to use reverse transcriptase to convert RNA --> DNA 

59

what enzyme does the herpes virus use to integrate into the host genome?

integrase 

60

what happens in the assembly phase of a virus?

viral proteins and copies of nucleic  acid are assembled 

61

how are the virions assembled during the assembly phase?

virions are formed by packaging the genomes with capsid proteins and if the virus is enveloped, by wrapping the nucleocapsid in an envelope

62

how are non-enveloped viruses released into the body once they get made in the infected cell?

when the cell dies, they get released

63

how are enveloped virions released into from the cell they got made?

by exocytosis

64

where do enveloped viruses acquire their lipid membrane?

at the cellular plasma membrane  or at the golgi by budding

65

what happens to the plasma membrane while the virus used budding?

virus takes a piece of the plasma membrane and pulling away a piece and eventually reducing the amount on the cell

66