Chapter 32—The Reception and Transmission of Extracellular Information
MULTIPLE CHOICE
1. Hormones and other signal molecules bind with ____ affinities to their receptors and are produced at
concentrations ____ their KD values.
a.
low; far above
b.
moderate; far above
c.
moderate; equivalent to
d.
high; far below
e.
very high; equivalent to
2. Steroid hormones, such as glucocorticoids, effect their action by:
a.
binding to a plasma membrane receptor, which stimulates a signal transduction pathway
within the cell
b.
binding to a plasma membrane receptor, which stimulates the receptor to enter the cell
c.
entering into the cell and affecting the production of secondary messengers
d.
entering into the cell and then acting as transcription regulators
e.
both a and d are correct
3. All are unifying features of polypeptide hormones EXCEPT that they are:
a.
originally synthesized with signal sequences.
b.
synthesized as inactive preprohormones.
c.
activated from preprohormones to hormones by phosphorylation.
d.
may produce several different peptide hormones with suitable processing.
e.
all are true.
4. Each of the following statements is true EXCEPT:
a.
epinephrine is an amino acid derivative
b.
steroid hormones can enter cells and regulate transcription
c.
insulin is a polypeptide hormone
d.
progesterone is a polypeptide hormone
e.
all of the above are true
5. The acrosome reaction, involving ion channel induced release of acrosomal enzymes used by sperm to
attack the egg, is induced by:
a.
estrogen.
b.
testosterone.
c.
dihydrotestosterone (DHT).
d.
progesterone.
e.
cortisol.
6. Which of the following doe NOT correctly pair a hormone with its function?
a.
ACTH − promotes production of thyroxin
b.
calcitonin − regulates plasma Ca2+
c.
FSH − stimulates processes within the gonads
d.
insulin − regulates metabolism and blood glucose
e.
prolactin − stimulates milk production
7. All are enzymes in the enzyme cascade for activation of glycogen phosphorylase EXCEPT:
a.
adenylyl cyclase.
b.
protein kinase A.
c.
hormone sensitive lipase.
d.
phosphorylase kinase.
e.
all are in the cascade.
8. G-proteins are associated with which receptor superfamily?
a.
oligomeric ligand-gated ion channels
b.
7-transmembrane segment (7-TMS) receptors
c.
cell adhesion protein receptors
d.
single-transmembrane segment catalytic receptors
e.
none of the above
9. All are components of the G-protein-coupled receptors (GPCRs) hormone signal transduction unit
EXCEPT:
a.
protein kinase A.
b.
adenylyl cyclase.
c.
hormone receptor.
d.
G-protein.
e.
all of the above.
10. Receptor tyrosine kinases have been called ____ as a result of their ____ and ____.
a.
membrane-associated allosteric enzymes; induced conformation changes; oligomeric
interactions
b.
adrenergic receptors; binding insulin; binding epinephrine
c.
GTP-binding proteins; GTPase activity; guanylyl cyclase activity
d.
multi-TMS receptors; complex structure; G-protein binding
e.
none of the above
11. All are domains of receptor tyrosine kinase EXCEPT:
a.
adenylyl cyclase activity domain.
b.
glycosylated extracellular receptor-binding domain.
c.
a single transmembrane -helix.
d.
intracellular tyrosine kinase domain.
e.
regulatory domain with phosphorylation sites.
12. The insulin receptor is in what class of tyrosine kinase receptors?
a.
Class I with 2 Cys-rich repeat sequences
b.
Class II with a2b2 tetrameric structure
c.
Class III with multiple immunoglobulin-like extracellular domains
d.
Class IV with a glycosylated protein domain
e.
Class V with a lipid-rich hydrophobic domain
13. How does extracellular hormone binding activate intracellular tyrosine kinase activity?
a.
conformational change induced active site activation
b.
conformational change induced oligomeric association and phosphorylation
c.
induced mRNA synthesis
d.
activation of specific phospholipases
e.
all are true
14. Nitroglycerine is a potent ____ because of the release of ____.
a.
antioxidant; O2
b.
vasoconstrictor; NO.
c.
vasodilator; NO.
d.
muscle tensor; O2
e.
all are true
15. In G-proteins, binding of GTP causes which of the following to occur?
a.
association of the G and G subunits with a receptor tyrosine kinase
b.
dissociation of G from the dimer formed by G and G
c.
phosphoylation of G using the GTP as the phosphorylating agent
d.
guanylation of G which promotes dissociation and activation of G
e.
none of the above
16. The binding of hormone to G-protein coupled receptor stimulates the sequence:
A.
binding of G (GTP) activates adenylyl cyclase
B.
G(GTP) dissociates and re-associates with G
C.
rapid exchange of GDP for GTP on G
D.
GTPase of G hydrolyzes GTP to GDP
E.
G dissociates from G
a.
B, C, A, D, E
b.
C, E, A, D, B
c.
C, E, B, D, A
d.
D, A, C, E, B
e.
E, A, D, B, C
17. The amount of cAMP generated in the cytoplasm is dependent on the:
a.
activity of adenylyl cyclase only.
b.
activity of the phosphodiesterase only.
c.
the length of time the GTP remains bound to the G-protein only.
d.
all of the above.
e.
none of the above.
18. A specific GTPase-activating protein (GAP) binds to and activates:
a.
the G-protein.
b.
the plasma membrane receptor.
c.
adenylyl cyclase.
d.
the GTPase activity of the Ras protein.
e.
none of the above.
19. G-proteins are involved in directly mediating the activity of the following EXCEPT:
a.
calmodulin.
b.
adenylyl cyclase.
c.
phospholipase C-.
d.
phospholipase A2.
e.
ion channels for K+ and other ions.
20. The hydrolysis of PIP2 by phospholipase C- yields what membrane-soluble secondary messenger?
a.
diacylglycerol (DAG)
b.
phosphatidylinositol (PI)
c.
phosphatidylinositol-4,5-bisphosphate (PIP2)
d.
inositol-1,4,5-trisphosphate (IP3)
e.
inositol-1,4-bisphosphate (IP2)
21. The second messenger produced from the hydrolysis of PIP2 that activates the increase of Ca++
concentrations in the cytoplasm is:
a.
diacylglycerol (DAG).
b.
phosphatidylinositol (PI).
c.
phosphatidylinositol-4,5-bisphosphate (PIP2).
d.
inositol-1,4,5-trisphosphate (IP3).
e.
inositol-1,4-bisphosphate (IP2).
22. Cancerous tumors may develop from all of the following EXCEPT:
a.
mutations in several proto-oncogenes or tumor suppression genes.
b.
interactions among two or more oncogene products.
c.
simultaneous mutations in a proto-oncogene and both copies of a tumor suppression gene.
d.
overlapping growth-control mechanisms that when one is compromised by mutation,
others take over.
e.
all are true.
23. Phospholipase C- is activated by ____ while phospholipase C- is activated by ____.
a.
receptor tyrosine kinase; G
b.
receptor tyrosine kinase; cAMP
c.
nitric oxide; G
d.
protein kinase A; cAMP
e.
none of the above
24. The phospholipid that is hydrolyzed to stimulate ceramide-activated protein kinase is:
a.
sphingomyelin.
b.
phosphatidylinositol-4,5-bisphosphate.
c.
phosphatidylinositol-4-phosphate.
d.
phosphatidylcholine.
e.
phosphatidylinositol.
25. Transient increases in cytoplasmic Ca2+ levels can activate all EXCEPT:
a.
muscle contraction.
b.
glucose uptake.
c.
exocytosis.
d.
glycogen metabolism.
e.
all are true.
26. All are results of the phospholipase C activity mediated by hormone binding, signal transduction and
eventually Ca++ release into the cytoplasm EXCEPT:
a.
an increase in guanylyl cyclase activity.
b.
the phosphorylation of specific proteins.
c.
activation of protein kinases by calcium complexed with calmodulin.
d.
the release of diacylglycerol from membrane phospholipids.
e.
the release of IP3.
27. Lithium salts have been used for years for the treatment of manic depression. Although its mechanism
of action at the molecular level is far from clear, it has been shown that Li+:
a.
alters the conformation of a number of plasma protein receptors.
b.
increases the GTPase activity of G-proteins.
c.
inhibits a number of enzymes in phosphoinositide metabolism.
d.
inhibits Ca++ release from cytoplasmic organelles.
e.
activates protein kinase A much like cAMP does.
28. Calmodulin exhibits all of the following characteristics EXCEPT:
a.
its conformation is sensitive to Ca++ binding.
b.
it contains a basic amphiphilic alpha helix which interacts with target proteins.
c.
it modulates the activity of many protein kinases.
d.
it contains one or more helix-loop-helix motifs (EF-hands) which bind the Ca++ ion.
e.
all are characteristics.
29. Calcium binding proteins all possess two or more characteristic peptide domains for Ca++ binding that
consist of a short -helix, a loop of 12 amino acids and a second -helix (helix-loop-helix) that is
called:
a.
basic region leucine zipper.
b.
zinc finger.
c.
EF hand.
d.
beta-beta.
e.
none are true.
30. Rapid influx of Ca++ into the cytoplasm can occur as a result of the binding of hormones to a receptor
activating phospholipase C activity. The increased level of Ca++ is derived from all of the following
EXCEPT:
a.
lysozymes.
b.
calciosomes.
c.
endoplasmic reticulum.
d.
extracellular stores through Ca++ channels in the plasma membrane.
e.
all of the above.
31. All are characteristic of EF-hand proteins EXCEPT:
a.
EF-hand domains usually are arranged so that two EF-hand domains directly contact each
other.
b.
EF-hand proteins dramatically change conformation upon binding Ca++ ions.
c.
Conformational changes promote binding of the EF-hand protein with its target protein(s).
d.
CaM (a EF-hand protein) binds target protein with basic amphiphilic alpha helix (Baa
helix) motifs.
e.
All are characteristic.
32. The members of the protein kinase C family that are regulated by Ca++, by diacylglycerol and by
phosphatidylserine are called the:
a.
atypical PKCs.
b.
conventional PKCs.
c.
modified PKCs.
d.
novel PKCs.
e.
all of the above.
33. The original phorbol esters are natural products that mimic ____ by binding and activating ____ that
potentiate the effects of ____.
a.
hormones; PKA; Ca2+
b.
DAG; PKC; carcinogens
c.
cAMP; PKA; glucagon
d.
Ca2+; PKC; Ca2+
e.
PIP2; CaM; Li+
34. ____ of Tyr527 in the SH2 domain of protein tyrosine kinase pp60c−src ____ tyrosine kinase activity by
moving an “activation loop” ____ the active site.
a.
Phosphorylation; activates; away from
b.
Phosphorylation; inhibits; into
c.
Dephosphorylation; inhibits; away from
d.
Dephosphorylation; activates; into
e.
none are true
35. In a neuron, when voltage-gated Na+ channels have just closed, which of the following is true?
a.
the membrane is less polarized than at rest
b.
the membrane is more polarized than at rest
c.
the membrane is polarized to the same degree as at rest
d.
the membrane is hyperpolarized
e.
none of the above are true
36. Which of the following statements regarding neurons and the action potential is NOT true?
a.
efflux of K+ ions leads to a brief hyperpolarization of the cell membrane
b.
the resting membrane potential is approximately −80mV
c.
sodium ions that enter an axon through sodium channels in a given axonal region diffuse
further along the axon, depolarizing the next axonal region
d.
in myelinated axons, sodium channels are distributed evenly
e.
all of the above are true
37. During an action potential, which of the following is directly responsible for restoration of resting
membrane potential?
a.
efflux of K+ ions
b.
efflux of Na+ ions
c.
influx of K+ ions
d.
influx of Na+ ions
e.
efflux of Cl− ions
38. Botulism toxin inhibits the potentiation of nerve impulses by interfering with what aspect of
acetylcholine signaling?
a.
prevents calcium channel opening, thus preventing the influx of calcium needed to release
acetylcholine
b.
prevents acetylcholine vesicles from fusing with the presynaptic neuronal membrane
c.
acts as an acetylcholinesterase to degrade acetylcholine in the synaptic cleft before it can
bind to receptors on the postsynaptic neuron
d.
binds to receptors on the postsynaptic neuron with very high affinity, preventing
acetylcholine from binding
e.
none of the above
39. Acetylcholinesterase:
a.
catalyzes synthesis of acetylcholine.
b.
is regulated by binding of cocaine.
c.
hydrolyzes acetylcholine inside the presynaptic cell.
d.
normally functions to prolong stimulation of the postsynaptic cell.
e.
must be secreted into the synaptic cleft.
40. All are inhibitors of acetylcholinesterase EXCEPT:
a.
sarin.
b.
malathion.
c.
parathion.
d.
tabun.
e.
all are inhibitors.
41. Neurotransmitters must be removed from the synaptic cleft to:
a.
promote prolonged stimulation of the postsynaptic cell.
b.
prevent prolonged stimulation of the presynaptic cell.
c.
promote prolonged stimulation of the presynaptic cell.
d.
prevent prolonged stimulation of the postsynaptic cell.
e.
none of the above.
42. Characteristics of myasthenia gravis include all EXCEPT:
a.
chronic disorder causing muscle weakness.
b.
autoimmune disease.
c.
individual’s antibodies bind their own acetylcholinesterase receptors.
d.
physiostigmine and neostigmine are used to treat myasthenia gravis.
e.
all are true.
43. Like acetylcholine, ____ and ____ are excitatory, but must be removed by ____.
a.
Asp; Lys; degradation
b.
Asp; Gly; reuptake
c.
Glu; Gln; reuptake
d.
Gln; Lys; degradation
e.
Lys; Arg; degradation
44. It is believed that many general anesthetics work by prolonging the open time of GABA receptors.
What type of channel does the GABA receptor mediate?
a.
sodium
b.
calcium
c.
chloride
d.
potassium
e.
all are true
45. The effects of ethanol on the brain arise in part from opening of ____ receptor Cl− channels.
a.
glycine
b.
aspartate
c.
glutamate
d.
-aminobutyrate (GABA)
e.
all are true
46. All are catecholamine neurotransmitters EXCEPT:
a.
-aminobutyrate (GABA).
b.
L-dopa.
c.
dopamine.
d.
epinephrine.
e.
norepinepherine.
47. Which of the following is correctly defined with regards to catecholamines?
a.
reserpine increases brain monoamine levels by upregulation of vesicle production
b.
bromocriptine is a dopamine antagonist linked to some Parkinson’s disease indidences
c.
cocaine binds to monoamine reuptake transporters on the presynaptic membrane thus
prolonging the effects of monoamines
d.
Prozac is a highly specific dopamine reuptake inhibitor
e.
none of the above
48. ____ act as an antidepressant by ____ levels of catacholamines in the brain.
a.
Tricyclics; increasing
b.
Tricyclics; decreasing
c.
Monoamine oxidase inhibitors; increasing
d.
Monoamine oxidase inhibitors; decreasing
e.
Monoamine oxidases; decreasing
49. A muscarinic receptor is a subclass of ____ receptor, and can be inhibited by ____.
a.
GABA; atropine
b.
GABA; acetylcholine
c.
acetylcholine; GABA
d.
acetylcholine; atropine
e.
acetylcholine; muscarine
50. Which of the following is not a peptide hormone?
a.
adrenocorticotropic hormone
b.
glucagon
c.
aldosterone
d.
calcitonin
e.
all of the above are peptide hormones
51. Which of the following is true regarding the GTPase activity of Ras proteins?
a.
under normal conditions, the GTPase activity is very high with most Ras proteins kept in
an inactive state
b.
Ras proteins have no inherent GTPase activity and rely upon the binding of GTPase-
activating protein
c.
mutations of the Ras protein cause GTPase activity to be extremely low
d.
the GTPase-activating protein is inhibited by cAMP
e.
none of the above
52. Across a normal cellular membrane, the potential is maintained with a positive charge on the outside
of the cell and a negative charge on the inside of the cell. Which of the following best explains the
operation of the voltage sensor in the voltage-gated sodium channel?
a.
Under resting cellular conditions, the voltage sensor is normally pulled to the inside of the
cell due to its high arginine content
b.
Under resting cellular conditions, the voltage sensor is normally pulled to the outside of
the cell due to its high lysine content
c.
When the membrane is depolarized, the voltage sensor moves towards the outside of the
membrane, allowing opening of the activation gate
d.
Both a and c occur
e.
None of the above
53. Which of the following is NOT an event that would occur upon the binding of a hormone to a
receptor?
a.
a second messenger such as cAMP might be produced
b.
inositol triphosphate causes the release of potassium from the ER
c.
protein kinase C is activated by DAG
d.
tyrosine kinase receptors dimerize and undergo phosphorylation
e.
all of the above occur
54. Which of the following is NOT a second messenger?
a.
cGMP
b.
norepinephrine
c.
nitric oxide
d.
diacylglycerol
e.
Ca2+
55. Which of the following is a G-protein coupled receptor?
a.
EGF receptor
b.
insulin receptor
c.
atrial natriuretic peptide receptor
d.
inhibitory 2-receptor
e.
EPO receptor