Brainscape's Knowledge GenomeTM

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


See full index

MICRO > Lecture 3 banfield > Flashcards

Lecture 3 banfield Flashcards

1
Q

what is an eclipse period

A

time between absorption of a virus to the cell and the appearance of infectious virus

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

what is a latent period

A

time between absorption of a virus and the release of new infectious virus from the cell

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

can latent period = eclipse period?

A

yes

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

what period typically ends first? latent or eclipse?

A

eclipse

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

true or false, viruses grow exponentially

A

false, they are released as single “burst”

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

what do viruses bind to on the outside of the cell? what kind of energy is normally required for this?

A
  1. glycoproteins
  2. carbohydrates (on ends of glycoproteins or glycolipids)
    normally this binding is an energy-independent process
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is multiple receptor use?

A

a single virus may bind more than one receptor on the cell surface (e.g. co-receptors)

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

what are the two penetration processes for viruses after attachment?

A
  1. endocytosis into intracellular vesicles called endosomes

2. fusion of the virus envelope with the cell membrane

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

t or f, unlike attachment, viral penetration requires energy and therefore the cell must be metabolically active

A

true

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

explain general fusion of viruses to cells (penetration)

A
  • only viruses with envelopes can do this
  • requires the presence of a specific fusion protein in the virus envelope!
  • requires energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

explain pH and virus fusion

A

virus fusion can be pH dependent (requires acidic endosome) or pH independent where it can occur at the cell surface or in an endosome

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

what kind of receptors aren’t typically virus specific

A

carbohydrates are less specific then protein receptors

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

what is fuzeon?

A

a antiviral drug that prevent HIV fusion (site of action of many drugs_

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

what is uncoating?

A

general term for what occurs after penetration; the capsid is fully or partially removed and allows viral genome to be exposed.

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

explain uncoating that occurs at the plasma membrane

A

viral membrane fuses at the cell membrane and releases capsid directly into the cytoplasm (the viral envelope becomes integrated into the PM).

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

explain uncoating within an endosome

A

rather than the virus “fusing” with the membrane it is engulfed by it and forms an endosome. This endosmoe then expels the capsid. low pH facilitates the endosome releasing the capsid

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

explain uncoating at the nuclear membrane.

A

virus is engulfed into an endosome into the cell. the endosome lyses before the nucleus where it docks the nuclear membrane. the viral genome is feed into the nucleus while the capsid is degraded / remains outside

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

explain the general process of a virus that attaches a cell, then penetrates via endocytosis and then un-coats at the nuclear membrane (6)

A
  1. binds carb or protein receptor
  2. is engulfed into an endosome
  3. acidic endosome begins to break down viral proteins
  4. acid-dependent endosome lysis occurs
  5. capsid uses microtubule transport to nucleus
  6. capsid binds and un-coating occurs. this allows viral genome to enter nucleus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the meaning of polarized microtubules?

A

microtubules allow larger component to move in the cell since the cytoplasm is dense. Polarized = (+/-) indicate the direction of movement

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

what kind of transport does herpes virus us use?

A

binds microtubules on the minus end. once at the nucleus, herpes capsids are packed with a lot of pressure which allows their genome to burst into the nucleus upon un-coating.

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

why does polio virus have a unique un-coating mechanism

A

polio virus is a non-envelope virus. it does not need to penetrate the cell at all. It simply binds the PM and injects its genome directly into the cytoplasm

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

How do most DNA viruses express their genomes?

A

they must use their - sense strand to produce mRNA (+). this transcription is done by RNA polymerase 2. which is located in the nucleus or brought with the virus (pox virus)

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

How would a + strand RNA virus express its genome?

A

these are already + strand mRNA!! they are directly translated
(retro virus is an exception that does not do this)

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

retroviruses are + strand RNA viruses but they do not immediately translate? what do they do?

A

they turn their +RNA to -DNA. then -DNA to dsDNA. this can incorporate into our genome which is why retroviruses are life long. . This dsDNA is transcribed by the -strand into +mRNA.

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

how do -RNA and dsRNA express their genome?

A

+mRNA must be made. To do this these enzymes use RNA-dependent RNA polymerase. Animal cells DO NOT contain these enzymes. therefore, -RNA and dsRNA MUST BRING IT WITH THEM.

26
Q

what RNA viruses are known to replicate through a DNA intermediate?

A

retroviruses

+RNA –> -DNA –> dsDNA –> +mRNA

27
Q

how do retroviruses make DNA from RNA?

A

they bring with them a reverse transcriptase enzyme.

28
Q

what is a provirus?

A

once a viruses genome integrates into the host genome it is called a provirus. Retroviruses use reverse transcriptase to make dsDNA. This integrates to form a provirus. RNA pol 2 then makes +mRNA.

29
Q

genome replication: ds DNA viruses (2 types)

A
  1. exclusively nuclear and uses cellular machinery

2. cytoplasmic (independent of cell machinery usually)

30
Q

Genome replication: ssDNA

A

occurs in nucleus where dsDNA intermediate is made first. thsis acts as a template to make multiple ssDNA.

31
Q

why do small DNA viruses often cause cancer?

A

they push cells into the cell cycle which increases the number of RNA polymerases which can lead to cell proliferation

32
Q

where do most RNA viruses replicate. What is the exception

A

RNA viruses typically replicate in the cytoplasm. Orthomyxoviruses are the exception

33
Q

how does +RNA viruses typically replicate

A

they immediately get translated into multiple proteins. One of these proteins will be an RNA-dependent RNA polymerase which will transcribe the +RNA into -RNA. this serves as a template for replication.

34
Q

there are two forms of +RNA replication. what are they?

A
  1. +RNA translates into a polyprotein that cleaves off into smaller ones. One of them transcribes the +RNA.
  2. +RNA is transcribed into -RNA. this creates subgenomic +mRNA’s which encode protein.
35
Q

what is the genome replication / expression for segmented

-RNA viruses

A

segmented RNA viruses –> the -RNA is used as a template to make mRNA. It is also used to replicate the whole genome into a +RNA. this is used as a template to make more -RNA.
the segmented mRNA that is made codes for 1 protein per segment

36
Q

what is the genome replication / expression for non-segmented -RNA viruses

A

non-segmented
-RNA viruses have one long piece of RNA. RNA dependent RNA polymerase synthesizes a bunch of subgenomic +mRNA molecules. each one makes a protein. the -strand is also turned into a + strand for replication

37
Q

what is the key difference between segmented and uni-molecular -RNA virus expression and replication?

A

uni - molecular –> one long - sense RNA which produces many subgenomic mRNA molecules to be transcribed into proteins (RNA-dependent RNA pol). it is also transcribed lengthwise for genome replication.

segmented –> The actual - RNA genome has multiple pieces, each codes for a protein (mRNA) and codes for a replicative transcript)

38
Q

what is the GP / NP small RNA?

A

an ambisense RNA

39
Q

how do GP/NP viruses work?

A

these are ambiviruses.

1) The - strand NP section gets transcribed into mRNA which is translated into a protein
2) replication of the RNA occurs which switches its polarity
3) now the GP region is transcribed and translated

40
Q

how do dsRNA viruses replicate and express?

A

the -RNA is synthesized into +RNA to be translated. another +RNA is made to be replicated. RNA-dependent RNA pol performs this.

41
Q

how does the virus ensure that only +mRNA is translated and not the + strand full-length complement too?

A

the mRNA in most viruses has a 5’ cap which initiates translation. The full complement +strand used for replication does not contain this .

42
Q

why do some viruses perform their replication in cell membrane?

A

they avoid the cell immune response from recognizing ds intermediates.

43
Q

what is virus assembly?

A

packaging of the genome into the capsid made by translated proteins

44
Q

what are the two ways assembly can occur with icosahedral capsids?

A
  1. the capsid is formed around the viral genome. (not well understood)
  2. the viral genome is fed into the pre-made capsid
45
Q

how does helical nucleocapsids assemble?

A

recall: helical capsids always have RNA genomes. the RNA genome is coated with nucleocapsid protein during synthesis which causes folding.

46
Q

what has 20 faces and 12 vertices?

A

icosahedral capsids. the vertices are either pentamers or hexamers (where the faces all meet)

47
Q

what are VP5 proteins and UL6?.

A

VP5 are the proteins that make up 11 hex and pent verticies of the Herpes (icosahedral) capsid. The UL6 protein is a portal which makes up the last verticie

48
Q

what is a pro-capsid?

A

capsid made before genome is added. Typically filled with scaffolding proteins

49
Q

explain the general herpes virus assembly progress

A

the translation of herpes genome creates many proteins. the first protein of the capsid is UL6 portal. then VP5 assembles the pent and hex vertices around this. a protease chews up scaffold proteins and permits herpes replicated genome to be fed into the capsid through UL6.

50
Q

what are inclusions?

A

a cytopathic effect (CPE) in which so many viral capsid proteins are made they form small clusters (inclusions) in the cytoplasm or nucleus.

51
Q

why are inclusions important?

A

the size and location of them are very characteristic pf different viruses.

52
Q

where are the inclusions found for herpes virus?

A

inside the nucleus

53
Q

what is egress?

A

exit of the virus from the cell

54
Q

how does naked virus egress occur?

A

poorly understood. Essentially the virus releases viroporins which disrupt the cell membrane and cause lysis. This permits exit of the virus and kills the cell.

55
Q

how do enveloped viruses egress?

A

through a process called budding –> they acquire an envelope from a variety of cellular membranes

56
Q

explain the two common budding envelopes

A
  1. viruses can bud with the PM and then be released directly
  2. viruses can bud with the golgi or the ER and then be secreted by the cell.
57
Q

explain the general process of herpes virus egress.

A
  1. nucleocapsid leaves nucleus by forming an endosome
  2. they then leave the perinuclear space by fusing with the perinuclear membrane.
  3. they then bud
    enter golgi by making an endosome. (acquired envelope)
  4. they then leave golgi b acquiring an outer membrane (nucleosome around a nucleosome)
  5. they then fuse their outer membrane with the PM and leave keeping their golgi body membrane
58
Q

when is the herpes virus considered infectious?

A

once it is delivered to the golgi body.

59
Q

how does HIV budding occur? why does this increase infectivity

A

budding occurs via cell to cell contact of T-cells. infectivity increases since upon budding the virus is directly transferred.

60
Q

how can some viruses transmit their newly formed virus directly from one cell to another?

A

the virus forms an envelope through budding. this gets modified to contain an actin tail. The exocytosis of the enveloped virus is then pushed by the actin tail directly into adjacent cells.

MICRO (28 decks)

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