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PMCOL 371 Lecture 10 Study Set Exam
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PMCOL 371 Lecture 10Study Set Exam
size of recpetors for ligand gated ion channels - Answer large, multisubunit proteins
speed of ligand gated ion channels - Answer very fast (can be submillisecond)
type of agonists - Answer small molecules
do receptors desensitize? - Answer yes after continued presence
weak presynaptic depolarization effect on presynaptic calcium current - Answer
gradual increase in curren
small tail currrent
strong depolarization effect on presynaptic calcium current - Answer no change in
current during depolarization (Vm > ECa)
large tail current causing short large conductance Ca influx
weak presynaptic depolarization effect on postsynaptic potential - Answer gradually lets
calcium to trigger NT release with delay between presynaptic step and EPSP
strong depolarization effect on postsynaptic potential - Answer onset of opening/depol
from repolarizing step is very quick
what channel is abundant in electrical organs of the torpedo fish - Answer nicotinic
acetycholine receptor (nAChR)
what blocks nAChR - Answer d-tubocurarine and alpha-bungarotoxin
structural properties of nAChR - Answer pentamer of 4 homologous subunits - 2 alpha, 1
beta, 1 gamma, one delta
whats special about the 2 alpha subunits - Answer carry a part of the binding sites for
alpha-bungarotoxin and ACh
exact speed of nAChR channel - Answer 0.3 msec
nAChR more likely to open when... - Answer ACh molecules bind to both binding sites
diameter of nAChR - Answer 0.65 nm
ion selectivity of nAChR - Answer cations
, what enzyme causes the termination of synaptic transmission for nAChR - Answer
Acetylcholinesterase (AChE)
nAChR mechanism of desensitization - Answer in continued presence of ACh, receptor
channel closes and adopts a conformation of high affinnity for ACh
agonist must unbind and receptor must rest to revert
binding of ACh to nAChR causes what conformation change - Answer rotation of
subunits to form open pore
how is recombinant nAChR channels made - Answer inject mRNA containing all
individual subunits into oocytes
oocytes synthesise receptor
can study channel now
homologous muscle nAChR (2 types) - Answer Muscle adult junctional receptor
embryonic and denervated
adult junctional receptor properties - Answer epsilon subunit ε
large conductance (60pS)
short burst duration
embryonic and denervated - Answer gamma subunit γ
lower conductance (40pS)
longer burst duration
homologous neuronal nAChRs - Answer stochiometry alphan betan?
blocked by K-bungarotoxin
chimeric receptors - Answer contructed by inserting the amino acid sequence of one
receptor into the corresponding region of another, or by substituting subunits from
other organisms
why are chimeric receptors studied - Answer possible to explore the functional
importance of different parts of the protein
what was found studying nAChR chimeras from subunits of mouse and torpedo - Answer
δ subunit appears to be important for channel properties
torpedo nAChR open time - Answer 8.6 ms
mouse nAChR open time - Answer 0.6 ms
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