Chapter ( ) - Viruses Flashcards
What is a host range? How is it determined?
The host range is how many number of host cells a virus can infect
it is determined based on the available receptors on cell surfaces
Viral genome composition (What molecules? How many strands? What arrangement/shape? How many genes)
ss/ds RNA
ss/ds DNA
genome either circular or linear
about 3 to 2,000 genes in the genome
What is a capsid
a protein shell that encloses the viral genome (built from protein subunits called capsomeres)
what is a lipid envelope? do all viruses have it
the lipid envelope is a coat of lipids that surrounds the protein coat
only some viruses have it
viruses can steal lipids from host cells as they leave the cell either from the plasma membrane or organelle membranes
a phage that only reproduces by lytic cycle is called
virulent phage
what is the lysogenic cycle? what is it called when phage can go thru lytic and lysogenic
no death to the host
temperate phages
crispr/cas
1) injected DNA gets cleaved
2) gets inserted to the crispr locus between repeat sequences spaced at regular intervals
3) crispr locus transcribed into pre-crRNA
4) processed into the cas proteins. each cas has a guide rna
5) cas nuclease finds a complement and destroys it
How viruses replicate 4 things (steps 2 and 3 interchangeable)
1) disassembly
2) replication of the viral genome
3) synthesis of viral proteins by viral machinery
4) reassembly of components into progeny viruses
disassembly (non-enveloped viruses - 2 ways)
pore formation (poliovirus)
1)binding
2) virus compartmentalized
3) genome threaded thru the endosome but endosome is not broken
endosomal membrane disruption (adenovirus)
1) binding
2)endosome
3) lysis of endosome
4) release of DNA (sometimes viral activity is carried out in the cytosol, other times in the nucleus)
disassembly (enveloped viruses lipid coat) HIV SPECIFICALLY (1/2 enveloped viruses)
1) hiv fuses its own lipid membrane with plasma membrane of cell
2) virus gets uncoated (disassembled)
disassembly (enveloped viruses lipid coat) influenza SPECIFICALLY (1/2 enveloped viruses)
flu doesnt fuse it binds
1) influenza binds epithelial cell of respiratory tract
2) influenza is wrapped in an endosome
3) acidifivation of endosome triggers fusion of lipid coat and endosomal membrane
4) influenza gets disassembled
enzymes pivotal for viral function (three) and how does highly active anti-retroviral therapy work
integrase (integrates genome into host cell genome)
protease (when the host cell receives the viral instructions for proteins it comes out as a linear polyprotein that needs to be cleaved into individual proteins)
reverse transcriptase (goes rna to dna)
HAART works by targeting these enzymes bc the virus has them
retrovirus pathway
1) fusion w plasma membrane
2) disassembly
3) reverse transcriptase takes ssrna and uses it as a template to make DNA (RNA-DNA hydrid)
4) dsDNA is made
5) integration of DNA (THIS IS CALLED PROVIRUS for phage it is a PROPHAGE )
6) self assembly and exit (THE VIRUS TAKES SOME OF THE LIPID MEMBRANE LOLOL)
what does neuraminidase do?
neuraminidase cleaves cialic acid residues on both the host cell and viral particle allowing it to leave the host
neuraminidase helps influenza leave
what does hemagglutinin do
functions as a receptor binding protein that mediates fusion with host cell
