Deck 11: The Reception and Transmission of Extracellular Information

Question 1

Hormones and other signal molecules bind with very high affinities to their receptors.At what concentrations are they produced in the body?

A)far above their KD values
B)not more than twice their KD values
C)equivalent to their KD values
D)far below their KD values

Answer 1

C

Question 2

Which of the following is NOT a part of the sequence involved with the binding of hormone to a G protein-coupled receptor?

A)Ga(GTP)dissociates and re-associates with Gbg.
B)The second messenger PKA is produced.
C)GTPase of Ga hydrolyzes GTP to GDP.
D)Binding of Ga (GTP)activates adenylyl cyclase.

Answer 2

B

Question 3

Which of the following components does a specific GTPase-activating protein bind to and activate?

A)the G protein
B)the plasma membrane receptor
C)adenylyl cyclase
D)the Ras protein

Answer 3

D

Question 4

Which of the following actions of nitroglycerine occurs when NO is released?

A)antioxidant
B)vasoconstrictor
C)vasodilator
D)muscle tensor

Question 5

Which of the following explains why receptor tyrosine kinases have been called membrane-associated allosteric enzymes?

A)as a result of their induced conformation changes and oligomeric interactions
B)as a result of their binding to insulin and epinephrine
C)as a result of their GTPase and guanylyl cyclase activities
D)as a result of their complex structure and G protein binding

Question 6

Which of the following does the amount of cAMP generated in the cytoplasm depend upon?

A)the amount of PKA present
B)the activity of phospholipase C
C)the amount of ATP
D)the length of time the GTP remains bound to the Ga protein

Question 7

Which of the following mechanisms do steroid hormones such as glucocorticoids use to effect their action?

A)by binding to a plasma membrane receptor and then entering the cell
B)by binding the plasma membrane receptor,which stimulates the receptor to enter the cell
C)by entering into the cell and effecting the production of secondary messengers
D)by entering into the cell and then acting as transcription regulators

Question 8

Which of the following classes of tyrosine kinases classifies the insulin receptor?

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

Question 9

Which of the following is a unifying feature of polypeptide hormones?

A)originally synthesized without signal sequences
B)synthesized as active prepro-hormones
C)may produce several different peptide hormones with suitable processing
D)activated from prepro-hormones to hormones by phosphorylation

Question 10

Which of the following regarding hormones is correct?

A)Progesterone is a polypeptide hormone.
B)Epinephrine is an amino acid.
C)Steroid hormones can enter cells and regulate translation.
D)Insulin is a polypeptide hormone.

Question 11

Which of the following steroids induces the acrosome reaction involving ion channel-induced release of acrosomal enzymes used by sperm to attack the egg?

A)estrogen
B)testosterone
C)dihydrotestosterone (DHT)
D)progesterone

Question 12

Which of the following second messengers is produced from the hydrolysis of PIP₂ that activates the increase of Ca²⁺ concentrations in the cytoplasm?

A)diacylglycerol (DAG)
B)phosphatidylinositol (PI)
C)phosphatidylinositol-4,5-bisphosphate (PIP2)
D)inositol-1,4,5-trisphosphate (IP3)

Question 13

Which of the following receptor superfamilies are G proteins associated with?

A)oligomeric ligand-gated ion channels
B)7-transmembrane segment (7-TMS)receptors
C)cell adhesion protein receptors
D)single-transmembrane segment catalytic receptors

Question 14

Which of the following is NOT a component of the G protein-coupled receptor (GPCR),hormone signal,transduction unit?

A)DAG
B)hormone sensitive lipase
C)membrane receptor
D)adenylate cyclase

Question 15

Which of the following membrane-soluble secondary messengers does the hydrolysis of PIP₂ by phospholipase C-b yield?

A)diacylglycerol (DAG)
B)phosphatidylinositol (PI)
C)phosphatidylinositol-4,5-bisphosphate (PIP2)
D)inositol-1,4,5-trisphosphate (IP3)

Question 16

Which of the following hormones is correctly paired with its function?

A)FSH: to stimulate processes within the gonads
B)ACTH: to promote production of thyroxin
C)calcitonin: to regulate plasma Na²⁺ and Ca²⁺
D)insulin: to regulate metabolism and proton concentration

Question 17

In G proteins,binding of GTP causes Gₐ dissociation.Which of the following effector proteins does it subsequently associate with?

A)adenylyl cyclase
B)GTPase
C)cAMP
D)Gg

Question 18

Which of the following explains how extracellular hormone binding activates intracellular tyrosine kinase activity?

A)by conformational change-induced active site activation
B)by conformational change-induced oligomeric association and phosphorylation
C)by induced mRNA synthesis
D)by activation of specific phospholipases

Question 19

Which of the following is NOT a domain of receptor tyrosine kinase?

A)adenylyl cyclase activity domain
B)glycosylated extracellular receptor-binding domain
C)intracellular tyrosine kinase domain
D)regulatory domain with phosphorylation sites

Question 20

Which of the following is directly modulated by G proteins?

A)calmodulin
B)adenylyl cyclase
C)phospholipase C-b
D)ion channels for K⁺ and other ions

Question 21

Which of the following do the original phorbol esters mimic?

A)hormones by binding and activating PKA,which potentiates the effects of Ca²⁺
B)DAG by binding and activating PKA,which potentiates the effects of carcinogens
C)cAMP by binding and activating PKA,which potentiates the effects of glucagon
D)PIP2 by binding and activating PKC,which potentiates the effects of Ca²⁺

Question 22

Which of the following is NOT activated by transient increases in cytoplasmic Ca²⁺ levels?

A)muscle contraction
B)glucose uptake
C)exocytosis
D)glycogen metabolism

Question 23

Which of the following is a characteristic of EF-hand proteins?

A)EF-hand domains usually are arranged so that 3 EF-hand domains directly contact each other.
B)EF-hand proteins dramatically change conformation upon binding Mg²⁺ ions.
C)CaM (an EF-hand protein)binds target protein with basic amphiphilic alpha helix (Baa helix)motifs.
D)Conformational changes promote dissociation of the EF-hand protein from its target protein(s).

Question 24

Rapid influx of Ca²⁺ into the cytoplasm can occur as a result of the binding of hormones to a receptor-activating phospholipase C activity.Which of the following does NOT contribute to the increased level of Ca²⁺?

A)lysozymes
B)calciosomes
C)endoplasmic reticulum
D)extracellular stores through Ca²⁺ channels in the plasma membrane

Question 25

Which of the following is NOT a result of the phospholipase C activity mediated by hormone binding,signal transduction,and eventually Ca²⁺ release into the cytoplasm?

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

Question 26

Which of the following is NOT involved in the generation of cancerous tumours?

A)mutations in several proto-oncogenes or tumour suppression genes
B)interactions among 2 or more oncogene products
C)simultaneous mutations in a proto-oncogene and only in 1 copy of a tumour suppression gene
D)overlapping growth-control mechanisms such that,when one is compromised by mutation,others take over

Question 27

Which of the following is a characteristic feature of acetylcholinesterase?

A)catalyzes synthesis of acetylcholine
B)regulated by binding of cocaine
C)hydrolyzes acetylcholine inside the presynaptic cell
D)must be secreted into the synaptic cleft

Question 28

Which of the following terms describes the members of the protein kinase C family that are regulated by Ca²⁺,diacylglycerol,and phosphatidylserine?

A)atypical PKCs
B)conventional PKCs
C)modified PKCs
D)novel PKCs

Question 29

Which of the following occurs when voltage-gated Na⁺ channels have just closed in a neuron?

A)The membrane becomes less polarized than when at rest.
B)The membrane becomes more polarized than when at rest.
C)The membrane becomes polarized to the same degree as when at rest.
D)The membrane becomes hyperpolarized.

Question 30

Which of the following is phospholipase C-g homologous to with respect to the X and Y domains?

A)phospholipase C-b
B)phospholipase C-a
C)phospholipase A2
D)phospholipase D

Question 31

Phosphorylation of Tyr⁵²⁷ in the SH₂ domain of protein tyrosine kinase pp60ᶜ⁻ˢʳᶜ inhibits tyrosine kinase activity.By which of the following mechanisms does it do this?

A)by moving an "activation loop" away from the active site
B)by moving an "activation loop" into the active site
C)by phosphorylating an "activation loop"
D)by covalent linkage to an "activation loop"

Question 32

Which of the following regarding neurons and the action potential is correct?

A)In myelinated axons,sodium channels are distributed evenly.
B)Influx of K⁺ ions leads to a brief hyperpolarization of the cell membrane.
C)The resting membrane potential is approximately -50 mV.
D)Sodium ions that enter an axon through sodium channels in a given axonal region diffuse further along the axon,depolarizing the next axonal region.

Question 33

Calcium-binding proteins all possess 2 or more characteristic peptide domains for Ca²⁺ binding that consist of a short a-helix,a loop of 12 amino acids,and a second a-helix (helix-loop-helix).Which of the following motifs best describes these peptide domains?

A)basic region leucine zipper
B)zinc finger
C)EF hand
D)beta-beta

Question 34

Which of the following reasons explains why neurotransmitters must be removed from the synaptic cleft?

A)to promote prolonged stimulation of the postsynaptic cell
B)to prevent prolonged stimulation of the presynaptic cell
C)to promote prolonged stimulation of the presynaptic cell
D)to prevent prolonged stimulation of the postsynaptic cell

Question 35

Which of the following phospholipids is hydrolyzed to stimulate ceramide-activated protein kinase?

A)sphingomyelin
B)phosphatidylinositol-4-phosphate
C)phosphatidylcholine
D)phosphatidylinositol

Question 36

Which of the following explains how botulism toxin exerts its effect?

A)by inhibiting acetylcholinesterase
B)by inhibiting acetylcholine release
C)by stimulating acetylcholinesterase
D)by opening ligand-gated ion channels

Question 37

Which of the following actions is directly responsible for restoration of resting membrane potential during an action potential?

A)efflux of K⁺ ions
B)efflux of Na+ ions
C)influx of K⁺ ions
D)influx of Na+ ions

Question 38

Lithium salts have been used for years for the treatment of manic depression.Which of the following describes the mechanism of action for Li⁺?

A)It alters the conformation of a number of plasma protein receptors.
B)It increases the GTPase activity of G proteins.
C)It inhibits a number of enzymes in phosphoinositide metabolism.
D)It inhibits Ca²⁺ release from cytoplasmic organelles.

Question 39

Which of the following is a characteristic of calmodulin?

A)It contains only 1 helix-loop-helix motif that binds the Ca²⁺ ion.
B)Its conformation is sensitive to Ca²⁺ binding.
C)It contains a basic amphiphilic alpha helix that interacts with target proteins.
D)It modulates the activity of only protein kinase A.

Question 40

Which of the following is NOT an inhibitor of acetylcholinesterase?

A)sarin
B)malathion
C)cortisol
D)tabun

Question 41

Which of the following amino acids are excitatory much like acetylcholine but must be removed by reuptake?

A)Asp and Lys
B)Asp and Gly
C)Glu and Gln
D)Gln and Lys

Question 42

Which of the following molecules is involved in the metabolic sequence for synthesizing epinephrine?

A)threonine
B)dopamine
C)acetylcholine
D)serotonin

Question 43

Which of the following molecule(s)is increased in the brain as a result of a monoamine oxidase inhibitor acting as an antidepressant?

A)insulin
B)tricyclics
C)catecholamine
D)tubulin

Question 44

It is believed that many general anesthetics work by prolonging the open time of GABA receptors.Which of the following types of channels does the GABA receptor mediate?

A)sodium
B)calcium
C)chloride
D)potassium

Question 45

Which of the following is NOT a catecholamine neurotransmitter?

A)g-aminobutyrate (GABA)
B)L-dopa
C)dopamine
D)epinephrine

Question 46

A muscarinic receptor is a subclass of acetylcholine receptor.Which of the following molecules inhibits the receptor?

A)muscarine
B)acetylcholine
C)GABA
D)atropine

Question 47

Which of the following receptor Cl- channels opens and contributes in part to the effects of ethanol on the brain?

A)glycine
B)aspartate
C)glutamate
D)g-aminobutyrate (GABA)