lecture 5 Flashcards
(36 cards)
what is a virus?
filterable agent that causes diseases –> semi permeable filter traps larger items like bacteria and allows smaller ones to pass thru
they are small enough to pass through a 0.2 micron filter
OR a set of genes in a protein coat
where is it replicated?
only in host, not in pure culture
what does it mean that some viruses are disease cofactors?
example?
some viruses that do not cause a disease themselves can increase the probability of a person getting that disease when present with a causing agent
KSHV–>causes Kaposi sarcoma, but does not develop KS unless the patient is infected wit HIV1 (cofactor)
do all viruses cause disease? what is an example?
no, some show symptoms (inapparent or subclinical) and some do not (asymptomatic)
SARS COVID2
are viruses alive?
are inert until they are in living cells
co op host cell machinery for their own replication
are obligate intercellular parasites
what is a virion and how does virion differ from virus?
what are two phases of a virus?
virion– viral particle is a physical set of genes in a protein coat – inert extraceullar form
virus can refer to type of virus or type of infection, or virion
virioin and infected cell–completely depended on the host
what are morphological features that make viruses different from cells?
small genome and either RNA OR DNA
are all smaller than the host they infect
what are virus replication properties?
do not grow or divide outside cells
don’t work outside cells (not alive)
lack energy generation systems
can’t make own proteins
replication depends on living cells
what is the virus replication process?
attach to cells randomly–> more likely to attach if virus and receptors are abundant & interaction is strong
enter cells–> likely to happen if internalization occurs upon virus/recpetor binding
use host machinery to replicate–> can fail if the cell lacks wha the virus needs
assemble and release
viruses are macromolecular assemblies that……
disassemble during replication
what are common capsid forms?
icosahral —polyhedron with 20 triangular faces
helical –capsomeres on viral nucleic acids, all helical animal viruses are enveloped
complex
what are types of viruses, that is their external surface of virons?
naked or enveloped –> both have virus proteins on external surface
enveloped
what is a capsid
protein coat surrounding viral genome
what is the difference between envelope and naked virus?
naked– lakes outer lipid bilayer, outside of virion is virus encoded protein capsid
envelope–lipid bilayer coating, acquired during budding thru a cellular membrane
what is a spike?
virion surface protein in viral genome
virion attachment proteins
can be called an envelope protein for some viruses
what is an asymptomatic infection?
disease virus undergoes replication, but disease symptoms do not occur so the individual may not know they are infected
what is a segmented genome?
genome that has more than 1 piece of nucleic acid
what is a viral antigen?
part of a virion whose structure is recognized by a host antibody
what is zoonosis?
infection of animals that spreads to humans directly or by an arthropod
why are enveloped virus less stable than naked?
lipid envelopes are fragile outside of bodily fluids
if envelope is removed, this will cause the enveloped virus to loose its proteins to attach to cells. because they are anchored to it
what are the 7 classes of viral genomes?
dsDNA
sDNA
dsRNA
ss + sense RNA
ss - sense RNA
gapped DNA
reverse transcribed RNA (ss + RNA with DNA intermediate AND gapped DNA)
what does plus and minus sense mean?
plus: sRNA that can be translated directly
minus: reverse complement of mRNA, complementary RNA serves as mRNA
what do large and small viral genome include?
large: genes redundant wit the hosts
alter host metabolism
genes for immune evasion
small: rely heavily on host
examples of dsDNA viruses?
herpes and epstein, small pox— evelope & large
HPV–nake and small
