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MIC 430 > Lec 2: Structure > Flashcards

Lec 2: Structure Flashcards

1
Q

Viral components: (3)

A
  1. ) nucleic acids
  2. ) capsid
  3. ) envelope (if enveloped)
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2
Q

(+)RNA –>

(-)RNA –>

A

(+)RNA –> can be directly used to synthesize protein

-)RNA –> compliment to (+

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3
Q

viroid =

A

small, self-replicating ss circular RNA molecule w/o protein coat

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4
Q

viroids are the smallest

A

infectious pathogens known

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5
Q

ALL known viroids…

A

infect higher plants

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6
Q

viroids often transmitted (2)

A

mechanically

& through pollen and seed

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7
Q

genome is packages in a protein structure known as a

A

capsid

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8
Q

many viruses also have a

which…

A

lipid component
which are generally present @ the surface of the virion forming an envelope (which also contains proteins with roles in aiding entry into host cells)

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9
Q

a few viruses form

A

protective protein occlusion bodies around their virions

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10
Q

Function of Viral Capsids: (2)

A
  1. ) protect viral genome

2. ) aid in entry of virus to a host cell

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11
Q

Naked virus structure:

A

capsid + genome = virion

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12
Q

Other viruses structure:

nucleocapsid =

A

(outer layer protein sometimes) + lipid envelope + capsid + genome = virion
nucleocapsid = capsid + genome

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13
Q

5 types of viral structure:

A 
Icosahedral
Enveloped Icosahedral
Helical 
Enveloped Helical
Complex
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14
Q

Virus genomes: (7)

*note:

A

ss, linear DNA
ds, linear DNA
ss, circular DNA
ds, circular DNA

ss, linear RNA
ds, linear RNA
ss, circular RNA

*note: NO ds circular RNA viral genome discovereed yet

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15
Q

How are virus genomes packed?

  • Some viruses:
  • Many viruses:
  • Some capsid proteins:
A
  • Some viruses: capsid protein coats the genome
  • Many viruses: nucleic acids bind inner part of capsid protein non-covalently (anchors DNA/RNA w/in capsid to avoid free-floating)
  • Some capsid proteins: have regions such as zinc finger that binds to nucleic acids
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16
Q

Human genomes =

Viral genomes =

A

chromosomes

segmented

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17
Q

most viruses consist of

but some…

A

a single molecule of nucleic acid

…but some have genes encoded in 2 or more nucleic acid molecules = segmented

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18
Q

segmented genomes are more common in

A

RNA viruses than DNA ones

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19
Q

some viruses package genome segments into…

while others package genome segments into…

A 
one virion  (ex: influenza virus)
separate virions  (ex: brome mosaic virus)
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20
Q

Brome Mosaic Virus contains…

A

3 types of particles that are physically & virtually indistinguishable:

  1. ) most dense (RNA1)
  2. ) least dense (RNA2)
  3. ) middle density (RNA3 & RNA4)
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21
Q

Why is segmentation favorable? (3)

but…

A

1.) allows virus to survive environmental pressure
2.) more potential for gene recombination
3.) faster evolution
…but for those who package genome into separate virion, at least one of each has to infect the same cell

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22
Q

(Capsid proteins)
Simple Virus =
Complex Virus =

A

= 1 protein type for capsid

= multiple protein types for capsid

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23
Q

capsid proteins are…

A

asymmetrical, but are organized to form symmetrical structures

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24
Q

many _____ viruses have helical symmetry

A

ssRNA

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25
Q

Helical symmetry:

A

RNA is coiled in the form of a helix and many copies of the same protein species are arranged around the coil forming an elongated structure

26
Q

helically symmetrical viruses can have rigid or flexible rods depending on

A

if strong or weak bonds are present between the protein molecules

27
Q

the length of the capsid is determined by

A

the length of the nucleic acid

28
Q

the symmetry of a capsid is based on

A

how you look @ it

29
Q

to construct icosahedrons, you need

A

different types of proteins

30
Q

to modify icosahedrons, you need

A

to add more proteins

31
Q

when constructing icosahedrons…

so…

A

it is impossible for all molecules to be arranged perfectly symmetrically with equivalent bonds,
…so there is the Quasi-Equivalence Theory

32
Q

Quasi-Equivalence Theory

A

the molecules of an icosahedron don’t interact exactly equivalently with e/o, but NEARLY equivalently

33
Q

General Bacteriophage Structure:

A

Icosahedral Head: stores DNA
Tail: transfers DNA
Tail Fibers: distinguish which bacteria is the host

34
Q

all tailed bacteriophages have _____ genome type

A

dsDNA

35
Q

many viruses have a _____ ________ component

A

lipid membrane component

36
Q

virus lipid membrane is typically associated with

A

virus protein

37
Q

virus lipid membrane + virus protein = ________, which….

A

envelope, which encloses the nucleocapsid (nucleic acid + capsid)

38
Q

most viruses get their membrane from _____, and this makes them
some viruses get their membrane from _____, and this makes them

A

budding out of cells = external

assembly step = internal

39
Q

virus membranes can be either

A

internal or external on the virion

40
Q

many animal viruses are

A

enveloped

41
Q

most of the proteins associated with the membranes of enveloped viruses are

A

integral membrane proteins

42
Q

most virion membranes are derived from

A

host cell membranes that undergo modification before incorporation into virions

43
Q

some viruses are able to replicate in

A

more than one kind of host

44
Q

progeny virions are released from cells; the lipid composition of the envelope may

A

reflect that of the host cell

45
Q

envelopes are obtained by

A

budding through a cellular membrane (except poxviruses)

46
Q

envelopes allow the possibility of

A

exiting the cell w/o killing it

47
Q

envelopes contain at least one

A

virally coded protein (for host attachment)

48
Q

loss of envelope =

A

loss of surface protein = loss/reduction of infectivity

49
Q

(envelope glycoproteins)
are =
function =
found =

A 
are = proteins modified by attachment to a sugar
function = recognition
found = on cell surface (firmly embedded in the envelope bilayer)
50
Q

envelope glycoproteins are firmly embedded

A

in the envelope bilayer

51
Q

envelope glycoproteins can form…

used for…

A

spikes or other structures on the outside of the virion used for attachment to host cell

52
Q

enveloped viruses are susceptible to

A

acid, detergents, etc

53
Q

occlusion bodies mostly found in

A

insect cell viruses

54
Q

occlusion bodies =

A

crystalline protein matrix (extra layer of protection) surrounding the nucleocapsid

55
Q

occlusion bodies are produced in the

A

nucleus or cytoplasm of infected cells

56
Q

occlusion bodies confer

A

resistance to adverse environmental conditions on the virus

57
Q

occlusion bodies are dissolved by

A

the alkaline pH of the insect gut, resulting in the release of infectious virus particles

58
Q

virus genome can only be…

but virions can have…

A

one type

different types of nucleic acids to help in replication

59
Q

DNA viruses contain…

& function…

A 
virus RNA (short RNA sequences covalently attached to DNA)
& function as primers for DNA synth & remain attached to the genome in the mature virion
60
Q

other cell molecules incorporated into virions:

A

tRNA
proteins
polyamines
cations

61
Q

polyamines & cations function in virions =

A

neutralize the negative charges on the virus genome

MIC 430 (22 decks)

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