Viruses Flashcards
percentage of infectious diseases that are from virus
60 %
viral infections cause or contribute to what percentage of human cancers
20%
are viruses microorganims
no they need host to survive - obligate intracellular
genomic material of virus
DNA or RNA but not BOTH
what viruses have both DNA and RNA
giant virus aka giruses
what is the core of virus
nucleic acid and protein coat
what is a virion and another name for it
completely infectious particle
viable virus
some properties of viruses
diversity is enormous
limited host range (usually only one cell type)
cell tropism
survival dilemma
what does virus having cell tropism mean
they will only infect certain types of cell
typical size of virus
typically 0.2 micrometers
what do you call viruses/virion that do not have an envelope
they are described as being naked
what is the capsid of virions made of and its importance
protein coat
protection
protein shell around nucleic acid is called
nucleocapsid
what do viruses need to make their proteins aggregate into a capsomer
nothing — self assembly
they do not need energy
two main types of capsid symmetry
helical icosahedral (perfectly stable structure)
most animal viruses and most viruses that cause diseases in human have what type of capsid
icosahedral
what do all human viruses with a helical capsid have
an envelope
describe the structure of a helical capsid
rigid or flexible
length controlled by NA
PS it goes NA –> capsomer (subunit of capsid) –> capsid
describe the structure of a icosahedral capsid
20 facets (each an equilateral triangle) 12 vertices because of the axes has 5:3:2 symmetry
what are the two different types of capsomers for icosahedrals
pentons - are at the points of the triangles aka vertices
hexons - make up the face of the equilateral triangle aka the facets
since all icosahedral capsids have 20 facets and 12 vertices, where does the size differential come from?
increasing the size of the hexons increases the size of the icosahedral capsid
what is the viral envelope composed of
2 lipid layers interspersed with protein molecules
virus does not have any lipid so where does it gets the lipid for its envelope
host
so where does the material for the viral envelope come from
host (lipid) and virus (proteins)
what does the viral envelope surround
nucleocapsid (baggy or shrink wrapped)
what type of infections are viral envelopes associated with
persistent infections
describe enveloped viruses interaction with alcohol and with the immune system
enveloped viruses have lipids so it is easy to eliminate them (more susceptible) with alcohols and once the surface protein on the envelope is eliminated, virus cannot carry out their function
on the other hand, enveloped viruses are harder to recognize by the immune system so that is its advantage
two major proteins on viral envelope of influenza virus
hemagglutinin (surface glycoprotein)
neuraminidase (surface spikes)
function of the viral envelope major proteins in influenza virus
Hemagglutinin (surface glycoprotein) - Attaches to sialic acid residues of host cell surface
Neuraminidase (surface “spike”) - Aids in release of virus from host cell
where are nucleoproteins found
core of virus
what is the function of nucleoprotein
required for replication strategies and to stabilize NA during replication
what type of function do nucleoproteins typically have
enzymatic
importance of matrix proteins
– Links envelope and capsid: stabilization
– Can drive final assembly process
– Important determinant of budding location
what are surface proteins
proteins that are exposed on the surface capsid or envelope proteins (glycoproteins) and help with attachment to host cells (includes VAPs)
shape of nucleic acid in virus
linear or circular or segmented
how are viruses classified
baltimore classification system
