Q: What reaction does the enzyme adenylyl cyclase catalyze?

$$\text{ATP} \rightarrow \text{cAMP}$$

Question 1

Which of the following best describes the correct order of signal transduction for the β-adrenergic receptor pathway?

Accepted Answer

Hormone → receptor → G protein → second messenger → kinase → cellular effects

Question 2

Which molecule is NOT involved in the signal transduction of the β-adrenergic GPCR pathway?

Accepted Answer

ATP

Question 3

What reaction does the enzyme adenylyl cyclase catalyze?

Accepted Answer

$$	ext{ATP} ightarrow 	ext{cAMP}$$

Question 4

A mutation prevents the G protein from hydrolyzing GTP. What is the most likely result?

Accepted Answer

Cellular levels of cAMP would stay high independent of ligand binding.

Question 5

Which of the following does NOT occur after ligand binding to a GPCR and activation of the cAMP cascade?

Accepted Answer

GTP dissociates from the G protein as adenylyl cyclase is activated.

Question 6

Which of the following is the correct sequence of events in the stimulatory adenylyl cyclase GPCR signaling pathway?

Accepted Answer

Ligand binds GPCR → G protein GDP/GTP exchange → G protein activation → Adenylyl cyclase activation → cAMP production → PKA activation

Question 7

What is the primary second messenger produced in the β-adrenergic GPCR pathway?

Accepted Answer

cAMP

Question 8

Which enzyme is directly activated by cAMP in the GPCR signaling pathway?

Accepted Answer

Protein kinase A (PKA)

Question 9

A researcher adds a non-hydrolyzable GTP analog to cells. What is the expected effect on the GPCR signaling pathway?

Accepted Answer

The G protein remains active, leading to prolonged cAMP production.

Question 10

Which of the following best explains why cAMP levels decrease after the removal of a ligand from the GPCR?

Accepted Answer

Phosphodiesterase hydrolyzes cAMP to AMP.

Question 11

Which step in the GPCR signaling pathway is responsible for signal amplification?

Accepted Answer

Activation of adenylyl cyclase by G protein

Question 12

A patient has a mutation in the gene encoding adenylyl cyclase, rendering it nonfunctional. Which of the following would be the most direct consequence?

Accepted Answer

cAMP is not produced in response to ligand binding.

Question 13

Which of the following is a direct effect of PKA activation in the cell?

Accepted Answer

Phosphorylation of target proteins

Question 14

Which of the following would most likely result from a loss-of-function mutation in the Gα subunit of the G protein?

Accepted Answer

Decreased activation of adenylyl cyclase

Question 15

Which of the following best describes the role of GTP in the GPCR signaling pathway?

Accepted Answer

GTP binding activates the G protein, which then activates adenylyl cyclase.

Adenylyl Cyclase GPCR Signaling Pathway: Mechanism and Regulation

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