Virology (columbo)

Question 1

what are the three basic function of a capsid?

Answer 1

protect the genetic material
aid entry into the cell
package viral enzymes

Question 2

what are the three general capsid types?

Answer 2

helical, icosahedral, or complex(combination of helical and icosahedral)

Question 3

helical virus

Answer 3

composed of multiple protein subunits packed into a helical arrangement with the genetic material coiled inside

Question 4

Icosahedral virus

Answer 4

composed of repeating subunits called capsomeres, which are composed of 5-6 individual protein structures called a protomer

Question 5

what makes up a capsomere?

Answer 5

5-6 protomers

Question 6

when a virus is encompassed in a host cells’ lipid membrane they are said to be what?

Answer 6

enveloped

Question 7

what are possible sources of an envelope?

Answer 7

plasma membrane
nuclear membrane
cytoplasmic membranes

Question 8

what holds the envelope to the capsid?

Answer 8

tegument or matrix proteins

* can also be involved with delivering viral genetic material/enzymes for replication

Question 9

RNA virus can have orientation of RNA

Answer 9

positive sense, negative sense, double stranded, or ambisense

Question 10

positive sense

Answer 10

the RNA virus can be directly translated into viral proteins (5’-3’)
-basically is mRNA

Question 11

negative sense

Answer 11

needs to form a complimentary strand to make a positive sense strand to make proteins (3’-5’)

Question 12

what are the 7 groups of the baltimore system?

Answer 12

1. DS DNA
2. SS DNA
3. DS RNA
4. SS +RNA
5. SS-RNA
6. SS +RNA with RT has DNA intermediate
7. DS DNA with RT

Question 13

what do viral cells rely on to reach host cells?

Answer 13

collision

Question 14

how to viruses attach to host cells?

Answer 14

via glycoproteins located on envelope or capsid, and target glycoproteins on host cell surface

Question 15

is a virion receptor and attachment site a 1:1 ratio?

Answer 15

nope, remember the cell membrane is fluid

Question 16

what determines the range of host/tissue specificity?

Answer 16

viral attachment proteins, thus a virus species will on infect certain cells or tissues

Question 17

what is the eclipse phase?

Answer 17

once the virus is inside a cell and the host immune system can no longer detect it

Question 18

antibodies for viruses prevent what step of a viral life cycle?

Answer 18

attachemnt

Question 19

what are the two ways that viruses get into the cells?

Answer 19

direct fusion

viropexis

Question 20

what is direct fusion?

Answer 20

viral attachement, protein mediated fusion of the viral envelope and plasma membrane, and results in the capsid directly entering the cell.
* therefore the viral envelope stays at the plasma membrane, and the nucleocapsid enters the cell

Question 21

what is viropexis?

Answer 21

receptor mediated endocytosis. once in the endosome the low pH causes fusion and release of nucleocapsid into the cytoplasm.
* viral envelope does enter the cell, but fuses with the host endosomal membrane NOT the plasma membrane

Question 22

naked capsid penetration

Answer 22

basically they enter through viropexis, but must disrupt the endosomal vesicle because they have no envelope to fuse with.

Question 23

SS DNA parvovirus replication

Answer 23

• DNA folds that allows replication to produce a series of repeated viral genomes called a concatemer, creating a long continuous mRNA via
• The concatemer is then cleaved into single viral genomic DNA prior to assembly

Question 24

DS DNA herpesvirus

Answer 24

• complex expression, alpha components, beta components, and gamma components
• latent phase-virus is replicated with host DNA
• lytic phase- when virus is in active replication
• can cause cancers due to DNA disruption

Question 25

herpes alpha component

Answer 25

alpha are made first and are transcription factors for beta components

Question 26

herpes beta component

Answer 26

beta proteins are helicases, primases, DNA polymerases that will drive viral replication and transcription of gamma components

Question 27

herpes gamma components

Answer 27

gamma component is the structural components

Question 28

SS + RNA virus
eg: picornaviurs, poliovirus, rhinovirus
usually replicate in cytoplasm

Answer 28

• RNA enters cell and makes viral proteins directly called a polyprotein precursor, which is later cleaved into functional parts.
• Some of these proteins make RNA replication enzymes, which make -RNA to make more +RNA
• as more +RNA are made they are transcribed and make more viral enzymes and proteins to allow formation of progeny.

Question 29

SS-RNA virus

eg: orthomyxovirues aka influenza

Answer 29

need to make comp +RNA to be read by host ribosome
*packs its own RNA dependent polymerase to make this happen
-can replicate in cytoplasm or nucleus
comp +RNA stands are produced and sent to cytoplasm to be translated or retained as a template to make further -RNA
-viral structural proteins made by viral RNA+ which are assembled with -RNA

Question 30

+ SS RNA with own reverse transcriptase

Answer 30

• bring own reverse transcriptase to make DNA
• from here it can be integrated into host by viral integrase and is said to be a provirus
• then viral mRNA can be made, and thus viral proteins to make more progeny

Question 31

how does assembly happen?

Answer 31

• in such a way to favor the incorporation of viral genomes.
• site specific on genome for initiation of protein assembly.
• process is energetically favorable

Question 32

naked viral egression

Answer 32

cause the cell to go through apoptosis by disruptions on protein synthesis/ and normal cell cycles.
-they keep the cell alive long enough to complete replication and then allow the cell to die to release the virus

Question 33

enveloped virus egression

Answer 33

need to acquire host membrane, therefore tend to proceed down the normal protein secretion pathways.

• they are then expelled either by exocytosis or more commonly via budding from the plasma membrane.
• *they are now accessible to the immune system and have become visable

Question 34

how to viral surface proteins get onto the host cell membrane?

Answer 34

the proteins are programmed to appear at the site where the envelope will form.