Deck 13: Cell Signaling

Question 1

Incre ase in IP3 levels is ass ocia te with

A) Gs mechanims
B) Gi mechanisms
C) Gq mechanisms
D) Go mechanisms
E) A and C are correct

Answer 1

C

Question 2

The fun ction o f PK A in G s m ech anis m s is to

A) Alter the activity of target p roteins by phosphorylating them at serine or threonine residues
B) Synthesize cAMP from ATP
C) Degrade cAMP
D) Activate proteins by directly binding to them
E) Catalyze the re-association of the a and þç sub units

Answer 2

A

Question 3

The signaling mechanism that converts an electrical signal on the surface of the cell to a Ca₂+ signal inside the cell is which of the following?

A) Ligand-gated channels (especially glutamate receptors)
B) Ryanodine rece ptors
C) IP3 receptors
D) Voltage-gated Ca₂+ cha nn els
E) Calmodulin-dependent protein kinase

Answer 3

D

Question 4

Increased cytosolic [Ca₂+] involved in signaling can originate from

A) Influx from the extracellular fluid through channels on the plasma mem brane
B) Efflux from the mitochondria into the cytosol
C) Efflu x fro m store s in the end opla sm ic reticu lum throu gh R yR or IP3 receptors
D) Release from binding sites within the cytosol
E) A and C are correct

Question 5

In a Gs mechanism, what enzyme is activated by the a sub unit?

A) GTP ase
B) Calmodulin-dependent protein kinase
C) Adenyly cyclase
D) Protein phosphatase
E) Both A and C are correct

Question 6

Ligand-gated channels

A) Are located only on post-synaptic mem branes
B) Are located only on pre-synaptic mem branes
C) Change their conductances upon ligand binding
D) Bind only high molecular weight proteins
E) Conduct on ly Na+ or K+

Question 7

The fastest way to get a signal from one place to another in the body is through

A) Endocrine signals moving through the blood B, Paracrine signaling molecules diffusing through the ECF
C) Action potentials moving along axons
D) Mechanical signals
E) Chem ical signals moving along axons

Question 8

Turn off of a Gs m echanisms requires

A) Activation of a
B) deg rada tion o f cAM P by cAMP phosph odiesterase
C) PKA activation
D) Protein phosphatase inhibition
E) Protein phosphorylation

Question 9

A signaling molecule that influences cells nearby the secreting cell is said to be

A) Autocrine
B) Paracrine
C) Endocrine
D) Neurocine
E) Neural

Question 10

IP3 in signaling mechanisms

A) Is released form phosphatidylinositol bisphosphate in the plasma m embrane
B) Is synthesized from inositol bisphosphate in the cytosol 2+
C) Bind s to IP 3 receptors on the ER, causing an Increase in cytosolic [Ca ]
D) Is the main signaling chemical in Gs m echanisms
E) Both A and C are correct

Question 11

Which of the following receptors DO NO T alter cAMP levels as a major mechanism of action

A) þ
B) þ
C) a
D) a
E) M 2 receptors

Question 12

A signaling molecule that is secreted into the blood and carried by the b lood to dis tan t tar ge t ce lls is said to be

A) Autocrine
B) Paracrine
C) Endocrine
D) Neurocine
E) Neural

Question 13

Increases in cytosolic [Ca₂+] can be involved in the signaling of all of the following EXCEPT

A) Stimulus-secretion coupling
B) Excitation-contraction coupling
C) Excitation-synthesis coupling
D) Calmodulin-dependent signaling
E) Direct activation of enzymes

Question 14

Increasing cytosolic [Ca₂+] is more useful as a signaling mechanism than Increasing [Na+] or [K +] or [C l-] because

A) Far fewer Ca₂+ ions need to flow because intracellular [Ca₂+] is so low
B) Ca₂+ can bind to specific proteins
C) Unlike the other ions, Ca₂+ can activate phosphorylation of proteins
D) The Increase in [Ca₂+] can be short-lived
E) All of the above

Question 15

Catalytic receptors

A) Bind ligands o n th e surface m em bra ne and alter s ub stra tes in the cyto so lic compartment
B) Are activated only by neurotransm itters
C) Are activated only by steroid hormones
D) Bind second messengers inside cells and alter substrates in the cytosol
E) Stimulate catabolism

Question 16

Turning off a G-protein coupled receptor requires

A) Dissociation of the ligand from the receptor
B) Hydrolysis of GTP by the a su bu nit
C) Re-association of the a subunit with the þç su bu nit
D) Re turn o f the a ctivate d pro teins to their ba sal s tate
E) All of the above

Question 17

W hat intracellular signaling molecule is Increased during the Gs signaling cascade?

A) IP3
B) 3',5' cyclic AM P
C) Ph osp hate
D) Ca₂+
E) GMP

Question 18

The fun ction o f cA MP in Gs m ech anis m s is to

A) Activate PKA
B) Activate calmodulin-dependent protein kinase
C) Inhibit protein phosphatases
D) Bind to the a su bu nit
E) Bind to the þç su bu nit

Question 19

The ste p im m ed iate ly follo win g th e b ind ing of a liga nd to a G -p ro tein co up led rec ep tor is

A) Dissociation of the a subunit from the þ and ç su bu nit
B) Activation of some protein by the a su bu nit
C) Exchange of GTP for GDP on the a sub un it
D) Hydrolysis of GTP by the a su bu nit
E) Exchange of GTP for GDP on the þç su bu nit

Question 20

A signaling molecule that influences the cell that secretes it is said to be

A) Autocrine
B) Paracrine
C) Endocrine
D) Neurocine
E) Neural

Question 21

Sm all m ole cu lar we igh t lipo ph ilic h or m on es us ua lly

A) Bind to surface m olecules and ac t through G-protein cou pled receptors
B) Bind to cytosolic or nuclear receptors and alter gene expression
C) Bin d to ca talytic rec ep tor s o n th e s ur fa ce s o f c ells
D) Directly activate channels on the surface mem brane
E) Bind to surface molecules and act through the JAK-STAT pathway

Question 22

Nu clea r rec epto rs tha t alter ge ne e xpr ess ion bin d to

A) m RN A po lyme ras e II
B) Response elements on the DNA
C) Introns
D) Exons
E) G-protein coup led receptors