BIOC 384 EXAM 3 UPDATED ACTUAL QUESTIONS AND
CORRECT ANSWERS
Question:
1. Match the receptor type with the correct functional
consequences of ligand binding and subsequent
receptor activation.
____Nicotinic acetylcholine receptor
____G protein-coupled receptor
____Receptor tyrosine kinase
____Tumor necrosis factor receptor
____Nuclear receptor
1. opening of the inner chamber to facilitate passive ion
transport.
2. binding to specific DNA sequences and activating
topoisomerase activity to remove negative supercoils.
3. binding to specific DNA sequences and transcriptional
regulation of downstream target genes.
4. GTP hydrolysis to form the active GDP-heterotrimeric
G protein complex.
5. autophosphorylation of the cytoplasmic tail and
binding of adaptor proteins to Tyr-P.
6. deprotonation of carboxyl groups in the inner chamber
to form ionic bridges with Na+ and K+ ions.
7. assembly of adaptor complexes through TNF receptor
associated death domain proteins.
8. GDP-GTP exchange and dissociation of the
heterotrimeric G protein.
9. dephosphorylation of Tyr residues in the cytoplasmic
tail by tyrosine kinases in the N-terminal domain.
10. activation of cysteine proteases as a result cleavage
by the receptor C-terminal caspase domain.
Answer:
__1__
Nicotinic acetylcholine receptor
__8__
G protein-coupled receptor
__5__
Receptor tyrosine kinase
__7__
Tumor necrosis factor receptor
__3__
Nuclear receptor
,Question:
2. What prevents hydrated Na+ and K+ ions from passing
through the nicotinic acetylcholine receptor channel in
the absence of acetylcholine?
Answer:
A ring of nonpolar amino acids in the interior chamber prevents the hydrated ions
from moving through the constricted channel.
Question:
3. Based on the Butowt, R. and von Bartheld, C.S. (2020)
paper:
a) what might explain why ~60% of COVID-19 patients do
not experience anosmia even though they experience
other symptoms of SARS-CoV-2 infection?
b) what might explain why ~10% of COVID-19 patients with
anosmia do not regain their sense of smell even after 3
months?
Answer:
a) The olfactory support cells were not infected and/or killed by the virus.
b) The stem cells needed to replenish olfactory support cells were killed.
, Question:
4. Put the following eight signaling events in the correct
order describing how glucagon binding to glucagon
receptors in liver cells increases blood glucose levels in
between meals.
___The GDP-bound heterotrimeric G protein binds to the
receptor.
____The G-alpha subunit binds to activates adenylate
cyclase.
____Production of cyclic AMP leads to activation of PKA.
____GDP is exchanged for GTP in the G-alpha subunit.
____The G-alpha and G-beta/gamma subunits dissociate.
____The C-terminal domain undergoes a conformational
change.
____Glucagon binds to the N-terminal domain of the
receptor.
____PKA phosphorylates downstream proteins that control
glucose export.
Answer:
_3__The GDP-bound heterotrimeric G protein binds to the receptor.
__6__The G-alpha subunit binds to activates adenylate cyclase.
__7__Production of cyclic AMP leads to activation of PKA.
__4__GDP is exchanged for GTP in the G-alpha subunit.
__5__The G-alpha and G-beta/gamma subunits dissociate.
__2__The C-terminal domain undergoes a conformational change.
__1__Glucagon binds to the N-terminal domain of the receptor.
__8__PKA phosphorylates downstream proteins that control glucose export.
CORRECT ANSWERS
Question:
1. Match the receptor type with the correct functional
consequences of ligand binding and subsequent
receptor activation.
____Nicotinic acetylcholine receptor
____G protein-coupled receptor
____Receptor tyrosine kinase
____Tumor necrosis factor receptor
____Nuclear receptor
1. opening of the inner chamber to facilitate passive ion
transport.
2. binding to specific DNA sequences and activating
topoisomerase activity to remove negative supercoils.
3. binding to specific DNA sequences and transcriptional
regulation of downstream target genes.
4. GTP hydrolysis to form the active GDP-heterotrimeric
G protein complex.
5. autophosphorylation of the cytoplasmic tail and
binding of adaptor proteins to Tyr-P.
6. deprotonation of carboxyl groups in the inner chamber
to form ionic bridges with Na+ and K+ ions.
7. assembly of adaptor complexes through TNF receptor
associated death domain proteins.
8. GDP-GTP exchange and dissociation of the
heterotrimeric G protein.
9. dephosphorylation of Tyr residues in the cytoplasmic
tail by tyrosine kinases in the N-terminal domain.
10. activation of cysteine proteases as a result cleavage
by the receptor C-terminal caspase domain.
Answer:
__1__
Nicotinic acetylcholine receptor
__8__
G protein-coupled receptor
__5__
Receptor tyrosine kinase
__7__
Tumor necrosis factor receptor
__3__
Nuclear receptor
,Question:
2. What prevents hydrated Na+ and K+ ions from passing
through the nicotinic acetylcholine receptor channel in
the absence of acetylcholine?
Answer:
A ring of nonpolar amino acids in the interior chamber prevents the hydrated ions
from moving through the constricted channel.
Question:
3. Based on the Butowt, R. and von Bartheld, C.S. (2020)
paper:
a) what might explain why ~60% of COVID-19 patients do
not experience anosmia even though they experience
other symptoms of SARS-CoV-2 infection?
b) what might explain why ~10% of COVID-19 patients with
anosmia do not regain their sense of smell even after 3
months?
Answer:
a) The olfactory support cells were not infected and/or killed by the virus.
b) The stem cells needed to replenish olfactory support cells were killed.
, Question:
4. Put the following eight signaling events in the correct
order describing how glucagon binding to glucagon
receptors in liver cells increases blood glucose levels in
between meals.
___The GDP-bound heterotrimeric G protein binds to the
receptor.
____The G-alpha subunit binds to activates adenylate
cyclase.
____Production of cyclic AMP leads to activation of PKA.
____GDP is exchanged for GTP in the G-alpha subunit.
____The G-alpha and G-beta/gamma subunits dissociate.
____The C-terminal domain undergoes a conformational
change.
____Glucagon binds to the N-terminal domain of the
receptor.
____PKA phosphorylates downstream proteins that control
glucose export.
Answer:
_3__The GDP-bound heterotrimeric G protein binds to the receptor.
__6__The G-alpha subunit binds to activates adenylate cyclase.
__7__Production of cyclic AMP leads to activation of PKA.
__4__GDP is exchanged for GTP in the G-alpha subunit.
__5__The G-alpha and G-beta/gamma subunits dissociate.
__2__The C-terminal domain undergoes a conformational change.
__1__Glucagon binds to the N-terminal domain of the receptor.
__8__PKA phosphorylates downstream proteins that control glucose export.
