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Cell Signaling Problem Set

Problem 10: Signaling Events

In a fight-or-flight response, epinephrine released by the adrenal glands binds to a membrane receptor on muscle cells. Which of the following events result from ligand binding?

A. G-protein is activated by binding GTP and causing adenylyl cyclase to produce cAMP.
B. The second messenger, cAMP, activates protein kinase A which inhibits glycogen synthetase blocking glycogen synthesis.
C. Protein kinase A activates phosphorylase kinase, which transfers a phosphate that activates glycogen phosphorylase. This leads to the breakdown of glycogen and the production of glucose-1-phosphate.
D. Glucose produced from glucose-1-P stimulates glycolysis, producing energy for muscle contraction.

All of the above.

Yes, the response to epinephrine in liver and muscle is an example of a cascade that causes a number of enzyme changes to insure that free glucose is available for glycolysis in muscle tissue.

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