Virus Structure and Function

Question 1

What is a virus?

Answer 1

Tiny obligate parasite that is unable to sustain itself and can’t replicate on its own. It is only made up of one kind of nucleic acid.

Question 2

What is the main purpose for the virus?

Answer 2

To deliver it’s RNA or DNA into a host cell so that it’s genes can be expressed by the host cell. Basically it wants to make more viruses.

Question 3

What are some differences between bacteria and viruses?

Answer 3

Viruses are very small compared to bacteria
Viruses can’t self replicate like bacteria
Viruses don’t have ribosome-Bacteria does (cellular machinery)

Question 4

What is the structure of a virus?

Answer 4

The outer portion is an envelope (not all viruses have this), and this envelope is made up of glycoproteins
There is also a capsid (protein shell that protects the nucleic acid of the virus)

Question 5

How does the virus envelope impact the virus’s stability?

Answer 5

The envelope makes the virus less stable. Viruses with envelopes can’t survive on tables and do not transmit well environmentally.

Question 6

What is the viral capsid?

Answer 6

It is the protein shell that provides structure and symmetry to the virus. It consists of identical protein subunits. They can be either icosahedral or helical or spherical

Question 7

Which nucleic acid is more likely to mutate in a virus?

Answer 7

Rna viruses are more likely to mutate because RNA is less stable than DNA

Question 8

How do you classify viruses?

Answer 8

The nature of the nucleic acid (RNA or DNA)
The symmetry of the capsid (helical or icosahedral)
The presence of an envelope? (yes or no)
The structure, size and morphology of the virus
The tissue or organ tropism (adenovirus, enterovirus or rhinovirus)

Question 9

What is the replication cycle of a virus?

Answer 9

Attachement
Entry and uncoating
Replication and assembly
Egress or virus release

Question 10

How does a virus attach?

Answer 10

Direct fusion
Endocytosis (receptor mediated maybe?)
Receptor mediate entry (HEP viruses)
Nucleic acid translocation (rarely)

Question 11

What is polymorphism?

Answer 11

Mutation at very high levels

Question 12

How does fusion work?

Answer 12

Fusion-virus directly fuses with the host plasma membrane and then the nucleic acid is released.

Question 13

How does endocytosis work?

Answer 13

internalized into a vacuole, transported into an endoscope and then the nucleic acid is released

Question 14

What is receptor mediated entry?

Answer 14

It is when specific receptors are used by the virus to gain entry into the host cell
Engagement of the receptors will often change the structure of the virus to also help it enter

Question 15

What stage do we mostly target when dealing with inhibition of viruses?

Answer 15

We have stuff to prevent binding of the virus, because if it never binds, then nothing ever happens. We can target each site to potentially interrupt viral replication

Question 16

What is the lytic life cycle?

Answer 16

Virus gets in cell, replicates then blows up
Clinically VERY apparent
Covid, flu, common cold, rhino virus

Question 17

What is the lysogenic life cycle?

Answer 17

The virus enters, encorporates itself into the cell
clinically silent
Herpes simplex virus, chicken pox, HPV
Can’t get virus again because it stays in your system

Question 18

What is dsDNA virus Replication?

Answer 18

when the viral DNA is transcribed to viral mRNA by the VIRAL polymerase
mRNA is then translated to make proteins and enzymes for the new virus particle production
Then it uses the host RNA polymerase to make RNA
Then the newly created DNA polymerase can replicate the virus DNA
Varicella zoster, parvo, Hep B, HSV 1 and 2

Question 19

Rna viral replication?

Answer 19

Some act directly on mRNA, and read on the ribosome, sometimes extra replication enzymes need to be brought in
Rotavirus, polio, West Nile, Hep A and C, Flu, Covid

Question 20

Words of wisdom from Prameet

Answer 20

Don’t get bit
Don’t get lit
Don’t do it
Don’t get hit
Don’t eat shit

Question 21

What is a latent infection?

Answer 21

It is the persistence of viral enemies (not infections visions) in host cells but there is no destruction of the infected host cell
Example, HSV develops latency in the sensory neurons

Question 22

What is a negative sense RNA virus?

Answer 22

It has to be converted to a positive stranded genome prior to mRNA and protein production
Uses viral RNA polymerase to make the positive strand

Question 23

What is a positive sense RNA virus?

Answer 23

RNA can be transcribed directly to mRNA and can be used to make proteins
SARS-CoV-2 and other coronaviruses

Question 24

What is a retrovirus

Answer 24

It is negatively stranded RNA, so to make protein it needs reverse polymerase enzyme (RNA to DNA, then back to RNA) to make a protein

Question 25

How do you detect something you can’t see?

Answer 25

Direct detection with an electron microscopy
Serology-look for antibiotics against a virus
PCR-amplifies DNA
Antigen detection-true positive, false negative

Question 26

Electron Microscopy

Answer 26

impractical and not very sensitive (can only tell what family, not the actual virus)

Question 27

Virus Culture

Answer 27

Growth in tissue culture, not all viruses can be cultured, is very slow

Question 28

Serologic Response

Answer 28

Detection of immune response by the host against the infectious agent
Detects specific immunoglobulin
Often can be used when the virus is at low levels soon after infection

Question 29

PCR

Answer 29

Find a specific segment of RNA or DNA

Question 30

Antigen Detection

Answer 30

Direct test on a patient
Detects for antibodies of the particular organisms (not sensitive but very specific