$$ \text{ATP} \rightarrow \text{cAMP} + \text{PP}_i $$

Question 1

Which enzyme is directly activated by the Gαs subunit in the β-adrenergic receptor signaling pathway?

Accepted Answer

Adenylate cyclase

Question 2

What is the immediate effect of GTP binding to the Gαs subunit in GPCR signaling?

Accepted Answer

Activation of adenylate cyclase

Question 3

Which of the following molecules acts as a second messenger in the β-adrenergic receptor pathway?

Accepted Answer

cAMP

Question 4

What is the role of protein kinase A (PKA) in the adenylate cyclase GPCR signaling pathway?

Accepted Answer

It phosphorylates target proteins to elicit cellular responses.

Question 5

Which of the following best describes the process by which the β-adrenergic receptor activates adenylate cyclase?

Accepted Answer

Binding of ligand to receptor causes GDP-GTP exchange on Gαs, which then activates adenylate cyclase.

Question 6

Which of the following is the correct sequence of events in β-adrenergic GPCR signaling?

Accepted Answer

Ligand binds receptor → Gαs exchanges GDP for GTP → Adenylate cyclase activation → cAMP production → PKA activation

Question 7

Which of the following statements about cAMP is correct?

Accepted Answer

cAMP is produced from ATP by the action of adenylate cyclase.

Question 8

What is the function of phosphodiesterase in the GPCR signaling pathway?

Accepted Answer

It hydrolyzes cAMP to AMP, terminating the signal.

Question 9

A patient is given a drug that inhibits adenylate cyclase. What is the expected effect on the β-adrenergic signaling pathway?

Accepted Answer

Decreased cAMP production and reduced activation of PKA.

Question 10

Which of the following equations correctly represents the conversion catalyzed by adenylate cyclase?

Accepted Answer

$$ 	ext{ATP} ightarrow 	ext{cAMP} + 	ext{PP}_i $$

Question 11

Which of the following is NOT a direct result of β-adrenergic receptor activation?

Accepted Answer

Hydrolysis of cAMP to AMP by phosphodiesterase

Question 12

If a mutation prevents Gαs from binding GTP, what would be the consequence for the signaling pathway?

Accepted Answer

Adenylate cyclase would not be activated, and cAMP levels would remain low.

Question 13

Which of the following best explains why cAMP is considered a 'second messenger'?

Accepted Answer

It relays signals from the cell surface to intracellular targets.

Question 14

A researcher adds a non-hydrolyzable analog of GTP to a cell. What is the most likely effect on the β-adrenergic signaling pathway?

Accepted Answer

Prolonged activation of Gαs and sustained cAMP production.

Question 15

Which of the following steps is necessary for the termination of the β-adrenergic GPCR signal?

Accepted Answer

Hydrolysis of GTP to GDP on Gαs

Question 16

Which of the following is a direct substrate for protein kinase A (PKA)?

Accepted Answer

Serine or threonine residues on target proteins

Question 17

Which of the following would most likely result from a loss-of-function mutation in adenylate cyclase?

Accepted Answer

Reduced cAMP levels and impaired cellular response to β-adrenergic stimulation

Question 18

Which of the following is the correct formula for the hydrolysis of cAMP by phosphodiesterase?

Accepted Answer

$$ 	ext{cAMP} ightarrow 	ext{AMP} $$

Question 19

Which of the following is a common misconception about the β-adrenergic GPCR pathway?

Accepted Answer

Adenylate cyclase is activated directly by the ligand.

Question 20

Which of the following is the primary function of the β-adrenergic receptor in the context of GPCR signaling?

Accepted Answer

To detect extracellular signals and initiate intracellular signaling cascades

Adenylate Cyclase GPCR Signaling: Mechanism and Key Steps

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