Viruses and defense against Viral Infection Flashcards
Viruses have a protein coat that is called a ?
capsid! - they have one to several 100 genes in the form of DNA or RNA inside the capsid.
most viruses surround themselves with a lipid rich coat called the ?
envelope! - either borrowed from the hose or made in the host cell cytoplasm.
are viruses living organism?
no ! - need host machinery to replicate , they don’t metabolize organic material. use ATP by the host !
viruses can be crystallized without loosing their ability to infect
how does a viral infection begin?
when a virus adsorbs to a specific chemical receptor site on the host. chemical receptor is usually a specific glycoprotein on the host. virus can’t infect if the specific receptor is not present. then the nucleic acid of the virus penetrates the cell . once inside the cell two possible paths exist for the virus : lytic infection or lysogenic infection
what is the lytic infection?
virus takes over the cell machinery and starts making new viruses. the cell may fill with new viruses until it lyses or bursts. the period from infection to lysis is called the latent period. a virus following a lytic cycle is called a virulent virus.
what is a lysogenic infection?
a virus in this cycle is called a temperate virus. the viral DNA can remain incorporated in the host DNA , the virus is said to be dormant or latent and is called a provirus. the dormant virus may become active when the host cell is under some type of stress.
most animal viruses enter the cell through receiptor mediated ______?
endocytosis
what is plus strand RNA?
Proteins can be made directly from RNA
Retroviruses have which enzyme ?
reverse transcriptase so they can make DNA from RNA
What is minus strand RNA?
this RNA is complement to mRNA and must be transcribed to plus strand RNA before being translated.
what are viroids?
small rings of naked RNA without capsid ! they only infect plants.
what are prions?
naked proteins. cause infections in animals. capable of replicating themselves without DNA or RNA.
How does the body fight viral infections?
with antibodies- they bind to viral protein with cytotoxic T cells , which destroy infected cells. envelope of the virus is borrowed from the host, but spike proteins protrude from the envelope.
changes in spike proteins in the virus
since RNA pol docent have proofreading, changes in spike proteins are common in RNA viruses.- so when the spike proteins change, the antibodies will fail to recognize them.
what is a vaccine?
injection of antibodies or an infection of nonpathogenic virus with the same capsid or envelope.
