Deck 32: The Reception and Transmission of Extracellular Information

Question 1

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

Answer 1

B

Question 2

The hydrolysis of PIP₂ by phospholipase C-β 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)

Answer 2

A

Question 3

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

Answer 3

C

Question 4

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.

Question 5

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.

Question 6

All are domains of receptor tyrosine kinase EXCEPT:

A) adenylyl cyclase activity domain.
B) glycosylated extracellular receptor-binding domain.
C) a single transmembrane α-helix.
D) intracellular tyrosine kinase domain.
E) regulatory domain with phosphorylation sites.

Question 7

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.

Question 8

The binding of hormone to G-protein coupled receptor stimulates the sequence:
A)binding of Gα (GTP) activates adenylyl cyclase
B)Gα(GTP) dissociates and re-associates with Gβγ
C)rapid exchange of GDP for GTP on Gα
D)GTPase of Gα hydrolyzes GTP to GDP
E)Gα dissociates from Gβγ

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

Question 9

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

Question 10

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).

Question 11

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 Gα-protein only.
D) all of the above.
E) none of the above.

Question 12

G-proteins are involved in directly mediating the activity of the following EXCEPT:

A) calmodulin.
B) adenylyl cyclase.
C) phospholipase C-β.
D) phospholipase A₂.
E) ion channels for K⁺ and other ions.

Question 13

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

Question 14

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

Question 15

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

Question 16

In G-proteins, binding of GTP causes which of the following to occur?

A) association of the Gβ and Gγ subunits with a receptor tyrosine kinase
B) dissociation of Gα from the dimer formed by Gβ and Gγ
C) phosphoylation of Gα using the GTP as the phosphorylating agent
D) guanylation of Gβ which promotes dissociation and activation of Gα
E) none of the above

Question 17

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

Question 18

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

Question 19

Hormones and other signal molecules bind with ____ affinities to their receptors and are produced at concentrations ____ their K_D values.

A) low; far above
B) moderate; far above
C) moderate; equivalent to
D) high; far below
E) very high; equivalent to

Question 20

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.

Question 21

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.

Question 22

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.

Question 23

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.

Question 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.

Question 25

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

Question 26

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.

Question 27

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.

Question 28

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.

Question 29

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⁺

Question 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.

Question 31

All are inhibitors of acetylcholinesterase EXCEPT:

A) sarin.
B) malathion.
C) parathion.
D) tabun.
E) all are inhibitors.

Question 32

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.

Question 33

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.

Question 34

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

Question 35

Calcium binding proteins all possess two or more characteristic peptide domains for Ca⁺⁺ binding that consist of a short α-helix, a loop of 12 amino acids and a second α-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.

Question 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

Question 37

____ of Tyr⁵²⁷ in the SH2 domain of protein tyrosine kinase pp60^c−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

Question 38

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

Question 39

Phospholipase C-γ is activated by ____ while phospholipase C-β is activated by ____.

A) receptor tyrosine kinase; Gα
B) receptor tyrosine kinase; cAMP
C) nitric oxide; Gα
D) protein kinase A; cAMP
E) none of the above

Question 40

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.

Question 41

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

Question 42

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

Question 43

The effects of ethanol on the brain arise in part from opening of ____ receptor Cl− channels.

A) glycine
B) aspartate
C) glutamate
D) γ-aminobutyrate (GABA)
E) all are true

Question 44

____ 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

Question 45

All are catecholamine neurotransmitters EXCEPT:

A) γ-aminobutyrate (GABA).
B) L-dopa.
C) dopamine.
D) epinephrine.
E) norepinepherine.

Question 46

Which of the following is a G-protein coupled receptor?

A) EGF receptor
B) insulin receptor
C) atrial natriuretic peptide receptor
D) inhibitory α₂-receptor
E) EPO receptor

Question 47

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

Question 48

Which of the following is NOT a second messenger?

A) cGMP
B) norepinephrine
C) nitric oxide
D) diacylglycerol
E) Ca²⁺

Question 49

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

Question 50

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

Question 51

Discuss the Ras protein and the effect of mutation on the ras genE.​

Question 52

Discuss the structure of the catalytic core of Protein Kinase A.​

Question 53

How are the receptors that mediate transmembrane signaling processes classified?​

Question 54

Explain how neurons communicate at cholinergic synapses.​

Question 55

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

Question 56

Explain the effect of depolarization on voltage-gated ion channels.​

Question 57

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

Question 58

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