Virus Structure and Function Flashcards
(30 cards)
What is a virus?
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.
What is the main purpose for the virus?
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.
What are some differences between bacteria and viruses?
Viruses are very small compared to bacteria
Viruses can’t self replicate like bacteria
Viruses don’t have ribosome-Bacteria does (cellular machinery)
What is the structure of a virus?
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)
How does the virus envelope impact the virus’s stability?
The envelope makes the virus less stable. Viruses with envelopes can’t survive on tables and do not transmit well environmentally.
What is the viral capsid?
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
Which nucleic acid is more likely to mutate in a virus?
Rna viruses are more likely to mutate because RNA is less stable than DNA
How do you classify viruses?
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)
What is the replication cycle of a virus?
Attachement
Entry and uncoating
Replication and assembly
Egress or virus release
How does a virus attach?
Direct fusion
Endocytosis (receptor mediated maybe?)
Receptor mediate entry (HEP viruses)
Nucleic acid translocation (rarely)
What is polymorphism?
Mutation at very high levels
How does fusion work?
Fusion-virus directly fuses with the host plasma membrane and then the nucleic acid is released.
How does endocytosis work?
internalized into a vacuole, transported into an endoscope and then the nucleic acid is released
What is receptor mediated entry?
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
What stage do we mostly target when dealing with inhibition of viruses?
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
What is the lytic life cycle?
Virus gets in cell, replicates then blows up
Clinically VERY apparent
Covid, flu, common cold, rhino virus
What is the lysogenic life cycle?
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
What is dsDNA virus Replication?
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
Rna viral replication?
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
Words of wisdom from Prameet
Don’t get bit
Don’t get lit
Don’t do it
Don’t get hit
Don’t eat shit
What is a latent infection?
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
What is a negative sense RNA virus?
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
What is a positive sense RNA virus?
RNA can be transcribed directly to mRNA and can be used to make proteins
SARS-CoV-2 and other coronaviruses
What is a retrovirus
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
