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MICRO > Banfield lecture two - viral structure > Flashcards

Banfield lecture two - viral structure Flashcards

1
Q

what is a Virion

A

The mature infectious viral particle

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2
Q

What is the capsid

A

The protein shell that encloses and protects the viral nucleic acid

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3
Q

what is a capsomere

A

the structural unit of the icosahedral capsid

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4
Q

what is the core

A

the internal part of the viral particle that contains the nucleic acid and closely associated proteins.

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5
Q

what is the nucleocapsid

A

the structure composing of the capsid and the viral nucleic acid or core
capsid –> encloses genetic info / core
nucleocapsid –> capsid + enclosed genetic info/core

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6
Q

what is the envelope

A

viral lipid-bilayer consisting of internal spike proteins

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7
Q

what are spike proteins?

A

viral glycoproteins the project outward from the viral envelope

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8
Q

Briefly explain the adenovirus (structure + viral infection)

A

causes pinkeye
has no envelope
icosahedral structure

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9
Q

Briefly explain the rhabdovirus (structure + viral infection)

A

causes rabies
enveloped
helical capsid

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10
Q

Briefly explain the coronavirus (structure + viral infection)

A

often causes common cold

spike proteins cause the corona fusion shape

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11
Q

Briefly explain the papovirus (structure + viral infection)

A

causes warts
no envelope
many capsomers forming a circular nucleocapsid

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12
Q

what are the two common capsids in viruses

A

helical capsids

icosahedral capsids

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13
Q

what is a naked virus?

A

a virus with no envelope

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14
Q

true or false, helical animal viruses are naked

A

false, no helical animal viruses are naked

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15
Q

What organisms commonly have helical capsids?

A

plant viruses and bacteriophages

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16
Q

enveloped animal viruses with helical capsids contain what kind of nucleic acid?

A

helical capsid animal viruses will ALWAYS HAVE RNA and never have DNA

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17
Q

True or false, many RNA viruses build nucleocapsids using helical symmetry

A

true

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18
Q

If an animal virus contains a helical capsid it contains what nucleic acid? is this animal virus enveloped or not?

A

naked helical viruses do not exist, therefore it has to be enveloped. Additionally, no helical animal viruses contain DNA. therefore the nucleic acid must be RNA

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19
Q

true or false, helical capsids are closed structures

A

false, they are open ended rods

20
Q

What is one well studied helical capsid virus

A

TMV –> tobacco mosaic virus

21
Q

what are the two types of helical capsids?

A

flexible helical capsids

rigid helical capsids

22
Q

Rhabdovirus is an example of what capsid?

A

a rigid helical capsid

rhabdovirus causes rabies

23
Q

Paramyxovirus is an example of what capsid? what does it cause?

A

a helical flexible capsid.

Paramyxovirus causes measles

24
Q

why are there no naked helical capsid animal viruses?

A

no envelope inhibits the diversity of the virus and allows the immune system to easily defeat the naked helical virus. Glycoproteins in an envelope increase immune evasion

25
Q

explain the icosahedral capsid

A

icosahedral capsids are twenty-sided structures that from a sphere. Each building block of the icosahedron is a triangle. Science world is an example of this.

26
Q

what are the different axises of the icosahedron? explain this genetic economy?

A

2-fold
3-fold
5-fold
this is an example of genetic economy since the icosahedron uses many triangle subunits to produce one larger triangle

27
Q

what kind of capsid does herpes simplex have?

A

spherical icosahedral capsid

28
Q

HIV is an example of what kind of virus? what capsid does it have?

A

HIV is a retrovirus

it has an “unusual” capsid in which is contains hex and pent units

29
Q

why do some viruses have envelopes and others do not?

A

Viruses that are enveloped will exits the cell they infect after budding through some extra - cytoplasmic membrane. Non-enveloped viruses leave the cell they infect through cell lysis which is terminal.

30
Q

true or false, envelope viruses must kill their host

A

false, envelope viruses bud with cellular membranes which permits them to leave without lysing the cell.

31
Q

what are three general functions of glycoproteins on the envelope?

A
  • entry and host range determination
  • assembly and egress (exit)
  • evasion of immune response
32
Q

What form of viruses often bud out of cells and do not lyse them?

A

retro viruses

33
Q

Breifly explain the budding mechanism of retro viruses?

A
  1. proteins are expressed by the virus RNA genome
  2. these proteins interact with RNA thats been exported out of the nucleus
  3. the proteins bind the plasma membrane an begin exocytosis while DNA gets packed into the leaving molecule
  4. once the full virus has left the intermolecular proteins form the capsid.
34
Q

explain the general process of non-envelope viruses

A
  1. the virus binds and enters
  2. transport via microtubules to ER
  3. incorporated into nucleus where modifications occur and virus transcription occurs.
  4. transcripts become translated
  5. proteins help assemble virus within the nucleus which then finally causes cell lysis.
35
Q

true or false, the viral genome can consist of RNA, DNA, or both.

A

false, it can contain one or the other, never both.

36
Q

what type of strand (+/-) is mRNA

A

always designated + strand since its info is directly translated

37
Q

what type of strand is the coding strand

A

the coding strand has the same polarity as the mRNA strand and therefore is also a + strand

38
Q

complementary strands to the RNA or coding DNA are?

39
Q

how would you synthesize a - strand?

A

by using a + strand as a template

40
Q

explain the characteristics / possibilities of viral DNA

A
  • can be linear or circular
  • can be ds or ss
    ss DNA can be either + or -
    polarity
  • in some cases it can partially double stranded and circular (hepatitis B)
41
Q

explain the characteristics / possibilities of viral RNA

A
  • can only be linear
  • ss or ds
  • can be + or - or ambisense (both polarities)
  • mono-partite (single piece of RNA) or multipartite (multiple genome segments)
42
Q

What type of genome does the common Flu virus have?

A

it has a multipartite RNA virus which all code for different proteins that assemble into a single protein.

43
Q

where do most DNA and RNA viruses replicate

A

DNA - nucleus

RNA - cytoplasm

44
Q

what exceptions are there to the location of replication for DNA and RNA viruses?

A

the flu virus is an RNA virus that replicates within the nucleus . Pox virus is a DNA virus that replicates in the nucleosome

45
Q

Pox virus has a ___ genome which replicates in the ___. Due to this it provides its own ___

A

DNA genome
cytoplasm
DNA polymerase

MICRO (28 decks)

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