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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

retrovirus replication

start with RNA--> makes DNA (reverse transcriptase)--> gets incorporated into our genome-->transcribed into RNA--> protein