Flashcards in Exam 3 Deck (290)
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1
-Infectious element containing nucleic acid and a protein coat
lacking protein synthesis and energy production machinery
-Replicates within living cells
virus
2
what nucleic acid do viruses use?
-DNA or RNA (only one)
-single-stranded or double-stranded
-May be associated with core proteins
*All have some sort of capsid or protein coat, it surrounds the nucleic acid
3
are viruses free living?
can you see them with a light microscope?
no!
No!
4
do antibodies work against viruses
No!
except nitazoxanide in a few circumstances
5
The _____ is made of lipids and surrounds the ____,
-can be destroyed by acid, alcohol, etc.
envelope
capsid
6
4 features that viruses lack compared to other microorganisms
CANNOT:
1. grow on non-living media
2. possess both DNA and RNA
3. possess ribosomes
4. are not antibiotic sensitive
7
Protein shell comprised of repeating polypeptide units called capsomeres
capsid
8
2 capsid shapes
1. spherical configuration
2. helical configuration
9
spherical configuration
nucleic acid surrounded by capsid. Usually icosahedral symmetry (20-sided)
– Synonym: cubic symmetry
10
helical configuration
nucleic acid interwoven among protein capsomeres; tubular structure
11
-Comprised of protein layer, lipid bi-layer, and glycosylated protein spikes (peplomers)
-Lipid bi-layer derived from host cell membranes
-Carbohydrates also host-derived
envelope
12
what viruses have an envelope
on ALL animal HELICAL viruses and on some spherical (icosahedral) viruses
13
Mature viral particle, i.e., nucleo-
capsid +/- envelope
virion
14
how are viruses separated into families?
1. nucleic acid type (RNA/DNA, Single/double stranded, continous/segmented)
2. size/shape/substructure
3. presence or absences of envelope
4. mode of replication
15
what DNA viruses are single stranded
Parvovirus (paroviridae)
16
what RNA viruses are double stranded
Reoviridae (causes rotovirus)
17
viral cultivation
1. in animals
2. in eggs (embryonic membranes)
3. tissue
*requires living cells
18
virus cultivation endpoint:
visible change to cells
cytopathogenic effect (CPE)
19
virus cultivation endpoint:
RBC clumping to free virus
hemagglutination
20
virus cultivation endpoint:
RBCs adhering to virus
hemadsorption
21
viruses are what type of pathogen
obligate intracellular pathogen
22
4 non-clutivation ways to detect viruses
1. electron microscopy
2. antigen detection (Fluorescent Ab, radioimmunossay, ELISA)
3. Nucleic acid detection (PCR, hybridization)
4. Antibody detection (serology)
23
Electron microscopy resolution for viruses
1-2nm
*visualizes individual virions
24
Viral infections stimulate what immune response?
host antibody responses
25
describe antibody response to viruses
- Antibody titers rise during the 3-4 weeks following infection
- A positive IgM assay or a 4-fold rise in IgG titer signify recent infection
- Low titers of IgG persist indefinitely
26
virus-cell infection cycle steps (7)
1. absorption/ attachment of virus to cell membrane
2. penetration and uncoating
3. transcription/translation of early proteins (regulatory proteins and enzymes, host ribosomes)
4. replication of NA
5. transcription/translation of late proteins (ie. structural proteins, enzymes)
6. assembly (nuclear vs. cytoplasmic)
7. release
27
what ways can viruses penetrate and uncoat their viral NA into a cell
-transport across cell membrane via bacteriophage
-fusion of envelope with cell membrane
-endocytosis (most animal viruses)
28
positive sense replication
RNA directly codes for a protein for a virus
29
negative sense replication
must base pair match to make its complement--> + RNA and then codes to make a protein
30
