Which molecule acts as a second messenger in the cascade by which epinephrine stimulates the activation of the enzyme glycogen phosphorylase in liver cells?
A) Adenosine
B) Caffeine
C) Citric acid
D) Cyclic AMP
E) Adenylyl cyclase

Question

Quizplus · Accepted Answer

Cyclic AMP is a common second messenger in many signaling pathways, including the one by which epinephrine activates glycogen phosphorylase in liver cells. When epinephrine binds to its receptor on the cell surface, it activates a G protein, which in turn activates adenylyl cyclase. Adenylyl cyclase then converts ATP into cyclic AMP, which acts as the second messenger and activates protein kinase A. Protein kinase A then activates phosphorylase kinase, which activates glycogen phosphorylase, leading to the breakdown of glycogen into glucose-1-phosphate. Therefore, choice D, cyclic AMP, is the correct answer.

Which Molecule Acts as a Second Messenger in the Cascade