BIOC20 - LECTURE 3 EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS VERIFIED
capsids with helical symmetry
- organized as helical tubes composed of identical, repeating subunits
- longer the genome, the longer the helical nucleocapsid
parameters that define symmetry of helical capsids
- # of subunits per turn (µ)
- displacement along the helical axis btw one capsid subunit and the next (p)
- pitch (P) is the distance along the axis corresponding to one turn
P = µ *p
virus envelopes
- derived from host cellular membrane
- the lipid bilayer has similar protein composition as the cellular membrane from which it
was derived from
- viral glycoproteins are embedded in the lipid bilayer. when viral proteins get embedded
they tend to exclude host cell proteins
budding
process by which viral envelopes are acquired at the cell membrane
permeability barrier
- prevents leakage and functions as a gateway btw external environment and viral
genome
, - when there is no envelope things are less tightly packed no - envelope = tightly
packed
example of a virus that budded from ER
Flavivirus has lower amounts of cholesterol which is similar in composition to the ER
membrane
viral glycoproteins and their characteristics
spikes that are inserted into lipid memb to form mature viral envelope
characteristics invlude a large glycosylated external domain (ECTODOMAIN),
hydrophobic transmembrane anchor domain, short internal tail
glycosylation of the external domain
- prevents dehydration of external surface of virus particles as glycosylation motifs
attract water
- reduces protein protein interactions to prevent viral aggregation
Type 1 integral membrane protein
amino terminus (N) on OUTSIDE of cell; carboxyl terminus on INSIDE
most viral envelope proteins are of this kind
Type 2 integral membrane protein
amino terminus on INSIDE of cell, carboxyl terminus on OUTSIDE of cell
signal sequence function on envelope protein
directs insertion into membrane
type 1 memb protein have N terminal signal seq that is cleaved by a peptidase when
inserted into memb
type 2 use the transmemb anchor as signal seq
WITH COMPLETE SOLUTIONS VERIFIED
capsids with helical symmetry
- organized as helical tubes composed of identical, repeating subunits
- longer the genome, the longer the helical nucleocapsid
parameters that define symmetry of helical capsids
- # of subunits per turn (µ)
- displacement along the helical axis btw one capsid subunit and the next (p)
- pitch (P) is the distance along the axis corresponding to one turn
P = µ *p
virus envelopes
- derived from host cellular membrane
- the lipid bilayer has similar protein composition as the cellular membrane from which it
was derived from
- viral glycoproteins are embedded in the lipid bilayer. when viral proteins get embedded
they tend to exclude host cell proteins
budding
process by which viral envelopes are acquired at the cell membrane
permeability barrier
- prevents leakage and functions as a gateway btw external environment and viral
genome
, - when there is no envelope things are less tightly packed no - envelope = tightly
packed
example of a virus that budded from ER
Flavivirus has lower amounts of cholesterol which is similar in composition to the ER
membrane
viral glycoproteins and their characteristics
spikes that are inserted into lipid memb to form mature viral envelope
characteristics invlude a large glycosylated external domain (ECTODOMAIN),
hydrophobic transmembrane anchor domain, short internal tail
glycosylation of the external domain
- prevents dehydration of external surface of virus particles as glycosylation motifs
attract water
- reduces protein protein interactions to prevent viral aggregation
Type 1 integral membrane protein
amino terminus (N) on OUTSIDE of cell; carboxyl terminus on INSIDE
most viral envelope proteins are of this kind
Type 2 integral membrane protein
amino terminus on INSIDE of cell, carboxyl terminus on OUTSIDE of cell
signal sequence function on envelope protein
directs insertion into membrane
type 1 memb protein have N terminal signal seq that is cleaved by a peptidase when
inserted into memb
type 2 use the transmemb anchor as signal seq
