$$\mathrm{ATP} \xrightarrow{\text{adenylyl cyclase}} \mathrm{cAMP} + \mathrm{PP_i}$$

Question 1

Which of the following is NOT a general feature of cell signaling systems?

Accepted Answer

Replication

Question 2

In the adrenaline signaling pathway, what is the role of adenylyl cyclase?

Accepted Answer

It converts ATP to cAMP, acting as the enzyme that produces the second messenger

Question 3

Which of the following best describes a second messenger in GPCR signaling?

Accepted Answer

A small intracellular molecule that relays signals from the receptor to target proteins

Question 4

What is the correct order of events in epinephrine (adrenaline) signaling via GPCRs?

Accepted Answer

Epinephrine binds GPCR → G-protein exchanges GDP for GTP → Adenylyl cyclase produces cAMP → cAMP activates PKA → PKA phosphorylates targets

Question 5

Which process contributes to the termination of the adrenaline signal?

Accepted Answer

Hydrolysis of cAMP by phosphodiesterase

Question 6

A patient is given propranolol, a β-adrenergic antagonist. What is the expected effect on the adrenaline signaling pathway?

Accepted Answer

Decreased activation of G-proteins and downstream signaling

Question 7

Which equation correctly represents the conversion catalyzed by adenylyl cyclase?

Accepted Answer

$$\mathrm{ATP} \xrightarrow{	ext{adenylyl cyclase}} \mathrm{cAMP} + \mathrm{PP_i}$$

Question 8

Which of the following is a direct effect of Protein Kinase A (PKA) activation in the adrenaline pathway?

Accepted Answer

Phosphorylation of serine/threonine residues on target proteins

Question 9

What is the structural hallmark of G-protein-coupled receptors (GPCRs)?

Accepted Answer

Seven transmembrane helices

Question 10

Which of the following best explains the concept of amplification in cell signaling?

Accepted Answer

A single ligand binding event leads to the activation of many downstream molecules

Question 11

A mutation prevents GTP hydrolysis in the Gα subunit of a G-protein. What is the most likely cellular consequence?

Accepted Answer

Prolonged activation of adenylyl cyclase and continuous cAMP production

Question 12

Which of the following is a function of accessory proteins such as GAPs in G-protein signaling?

Accepted Answer

They increase the rate of GTP hydrolysis, promoting signal termination

Question 13

Which of the following is a real-world example of a signal to which cells respond, as listed in the study materials?

Accepted Answer

Antigens

Question 14

What is the effect of cholera toxin on G-protein signaling?

Accepted Answer

It inactivates GTPase activity, causing persistent activation of adenylyl cyclase

Question 15

Which of the following is NOT a direct effect of epinephrine signaling in muscle cells?

Accepted Answer

DNA replication

Question 16

Which equation represents the hydrolysis of cAMP by phosphodiesterase?

Accepted Answer

$$\mathrm{cAMP} + \mathrm{H_2O} \xrightarrow{	ext{phosphodiesterase}} \mathrm{AMP}$$

Question 17

Which protein is responsible for dephosphorylation of target proteins in the adrenaline signaling pathway?

Accepted Answer

Phosphoprotein phosphatase

Question 18

Which of the following best describes the role of AKAPs in the adrenaline signaling pathway?

Accepted Answer

They keep the signaling pathway localized by anchoring key proteins

Question 19

Which of the following is a plausible consequence of desensitization of the β-adrenergic receptor?

Accepted Answer

Reduced cellular response to repeated epinephrine stimulation

Question 20

Which of the following is a reason why GPCRs are major drug targets?

Accepted Answer

They are involved in a wide variety of physiological processes and diseases

Cellular Signaling: Adrenaline and G-Protein-Coupled Receptors (GPCRs)

Study Guide - Practice Questions