Viral Structure and Multiplication Flashcards
(83 cards)
1
Q
are viruses cellular or acellular?
A
acellular
2
Q
describe extracellular viral activity
A
inactive
3
Q
describe intracellular viral activity
A
activate by hijacking host
4
Q
how do viruses exist intracellularly and what do they do?
A
exists as nucleic acid, comandeer host cell
5
Q
describe 4 overview things that viruses are
A
- major cause of disease
- important members of aquatic world
- importantin evolution
- important model systems in molecular biology
6
Q
are viruses all bad?
A
no, they aare also important as sources of therapy
7
Q
how are virsus used as a source of therapy?
A
use viral mechanisms with desired added genetic material
8
Q
how are viruses important members of the aquatic world?
A
they move organic matter from particulate to dissolved
9
Q
how are viruses important in evolution?
A
they transfer genes between bacteria, others
10
Q
what are bacterial viruses called? (2)
A
- bacteriophages
2. phages
11
Q
are there a lot of archaeal viruses?
A
no
12
Q
what cells do most viruses infect?
A
eukaryotic
13
Q
what 5 things are viruses classified into families based on?
A
- genome structure
- life cycle
- morphology
- genetic relatedness
- enveloped or non-enveloped
14
Q
give a bacterial comparison point for the size of most viruses
A
most are 1/100th the size of E.coli
15
Q
can viruses be seen with regular microscopes?
A
no, need an electron microscope
16
Q
what are some of the largest animal viruses?
A
pox viruses
17
Q
approx howsmall are most viruses?
A
20nm in diameter
18
Q
what do all viruses contain?
A
a nucleocapsid which is composed of: nucleic acid (DNA or RNA) and a protein coat
19
Q
what are capsids?
A
large macromolecular structures which serve as protein coat of virus
20
Q
what is the role of capsids?
A
protect viral genetic material and aid in its transfer between host cells
21
Q
what are capsids made of?
A
protein subunits called protomers
22
Q
what are the 3 capsid shapes?
A
- helical
- icosahedral
- complex
23
Q
describe the shape of helical capsids
A
shaped like hollow tubes with protein walls
24
Q
what determines the length of a helical capsid?
A
amount of nucleic acid
25
how to protomers assemble in a helical capsid?
self-assemble
26
describe the shape of an icosahedral capsid
regular polyhedron with 20 equilateral faces and 12 vertices (soccer ball with faces)
27
what are capsomers in icosahedral capsids?
ring or knob-shaped units made of 5 (pentons) or 6 (hexons) subunit capsomers
28
give 2 examples of complex viruses
1. pox virus
| 2. large bacteriophages with binal symmetry
29
describe the binal symmetry of large bacteriophages (complex viruses)
head resembles icosahedral, tail is helical
30
what is a viral envelope?
an outer, flexible membranous layer that binds together many viruses
31
what are animal virus envelopes made of and what do they normall arise from?
lipids and carbohydrates, from host cell plasma or nuclear membranes, acquired as virus leaves host
32
what do some viral envelopes contain, and what are they often used for?
enzymes, often used for replication of the genome
33
describe viral envelope proteins?
evelope proteins, which are viral encoded, may project from the envelope sirface as spikes or peplomers
34
list the 4 functions of viral envelope proteins
1. involved in viral attachment to host cell
2. used for indentification of virus
3. may have enzymatic or other activity (ex. neuramimidase of influenza virus)
4. may play a role in nucleic acid replication
35
list and describe the 4 variations of genetic material a virus can have
1. ssRNA: single-stranded RNA
2. dsRNA: double-stranded RNA
3. ssDNA: single stranded DNA
4. dsDNA: double stranded DNA
36
is the length of nucleic acid in all viruses the same?
no, it varies from virus to virus
37
what are the two types of genomes a virus can have?
1. linear
| 2. circular
38
is virus genome always in one piece?
no, viruses can also have segmented genomes
39
what does the mechanism of viral multiplication depend on? (2)
1. viral structure
| 2. genome
40
what are the 5 common steps of viral multiplication?
1. attachment to host cell
2. entry and uncoating of genome
3. synthess
4. assembly
5. release into environment
41
what does step 1 of viral multiplication (attachment or adsorption) depend on?
specific receptor attachment
42
list the 3 mechanisms that the receptor determines host preference in the attachment step (step 1) of viral multiplication
1. may be specific tissue (tropism)
2. may be more than one host
3. may be more than one receptor
43
describe step 2 (entry into host) of viral multiplication (2)
1. entire genome or nucleocapsid enters
| 2. varies between naked or enveloped virus
44
what are the 3 methods of entry into the host used by viruses in viral multiplication?
1. fusion of the viral envelope with host membrane; nucleocapsid enters
2. endocytosis in vesicle; endosome aids in viral uncoating
3. injection of nucleic acid
45
what two entry mechanisms do enveloped viruses use in multiplication?
1. fusion
| 2. endocytosis
46
what entry mechanism do non-enveloped (NAKED) viruses use in multiplication?
injection of nucleic acid
47
describe the synthesis stage of viral multiplication
stage where all viral components are produced
48
what dictates the events that occur in the synthesis stage of viral multiplication?
the genome
49
what are the two options the genome can choose from in the synthesis stage of viral multiplication?
1. dsDNA typical flow: intructions, replication, blah blah blah
2. RNA viral flow
50
what do RNA viruses need to do for the synthesis stage of replication?
they must carry in or synthesize the proteins necessary to complete synthesis
51
in the synthesis stage of viral replication, list and describe the 3 types of genes
1. early genes: coding for synthesis proteins
2. middle genes: coding for protein parts of virus
3. late genes: involved in assembly
52
describe the assembly stage (step 4) of viral replication
putting all components together to make complete virions
53
is the assembly stage of viral replication simple or complex?
very comples
54
give an example of the assembly stage of viral replication
the baseplate, tail fibers, and head components of bacteriophage T4 (the spooky one) are assembled separately
55
what are the two types of virion release (step 5 of replication)?
1. non-enveloped virus lyse the host cell
| 2. enveloped viruses use budding
56
how do non-enveloped viruses lyse the host cell upon virion release?
they may attack peptidoglycan or membrane
57
what happens to the host cell as a non-enveloped virus leaves?
it is destroyed
58
describe the 4 steps of the budding process used by enveloped viruses in step 5 of replication
1. viral proteins are incorporated into host membrane
2. nucloecapsids may bind to viral proteins
3. enveloped derived from host plasma membrane, but may take Golgi, ER, or other structures too
4. virus may use host actin tails to propel through host membrane
59
what are the 2 types of phages in bacterial and archaeal infections in terms of reproductive choices?
1. temperate phage
| 2. virulent phage
60
how many reproductive choices do virulent phages have?
one
61
what reproductive choice do virulent phages follow?
multiply immediately upon entry, lyse bacterial host cell
62
how many reproductive choices do temperate phages have? what are they?
two
1. reproduce lytically as virulent phages do
2. remain within host cell without destroying it
63
what do many temperate phages do with their genome?
integrate their genome into host genome, becoming a prophage in a lysogenic bacterium, in a relationship called lysogeny
64
what is the lytic cycle?
makes active phages
65
what is the lysogenic cycle?
when host multiplies, phage multiplies with it, integrates genome into host, dormant phage
66
what would be the advantage of a virus having a lytic cycle?
conditions are good now! make more active guys fast! don't have to worry about host death before replicating
67
what would be the advantage of a virus having a lysogenic cycle?
conditions aren't where the virus wants, so they wait, or virus has infected all surrounding hosts due to lytic cycle, so enters lysogenic instead
68
in viral infection in eukaaryotic cells, what does cytocidal infection result in?
cell death through lysis
69
in eukaryotes, how long can persistent infections last?
years
70
what are CPEs?
cytopathic effects, structural effects of viruses
71
give 2 cytopathic effects of viruses on eukaryotic cells
1. degenerative changes
| 2. abnormalities
72
what can viral infection of a eukaryotic cell do to that cell?
transform it into a malignant cell
73
what are the 4 fuck-em-up options available to viruses after penetration of a eukaryotic cell?
1. transformation into a malignant cell
2. chronic infection
3. latent infection
4. rapid multiplication
74
what gets a virus from latent infection to rapid multiplication after penetration of a eukarytoic cell?
activation
75
what can happen after rapid multiplication after a virus penetrates a eukaryotic cell?
acute infection
76
what are prions?
proteinacous infectious particles, made ONLY of protein
77
what do prions do?
cause a variety of neurodegenerative diseases in humans and animals
78
list 3 diseases caused by prions
1. scrapie in sheep
2. bovine spongiform encephalopathy (BSE) or Mad Cow Disease
3. Kuru and Cretzfeldt-jakob disease
79
what is the broad category of diseases caused by prions called?
TSE (transmissible spongiform encephalopathies)
80
what is the current pathogenesis of diseases caused by prions?
normal prion proteins exist around neural cells, and when exposed to abnormal proteins they convert normal proteins to abnormal proteins, which alters or blocks a lot of neural function
81
what symptoms are caused by most prions?
brain lesions, behavioral changes, loss of motor functions
82
is there a cure for diseases caused by prions?
no cure because the mechanism is not yet fully understood
83
list and describe 2 additional subviral agents
1. viroids: infectious agents comprised of only RNA, target plants
2. satellites: infectious agents composed of nucleic acids and a protein coat, need a co-infector (virus) to replicate, can infect plants and animals
