BCH 4054 October 8, 1999 HOUR TEST 2 NAME_____________________ Points 1. The stimulation of glycogen breakdown by hormones was the first experimental system in which a "second messenger" signaling pathway was demonstrated for the ultimate activation of the enzyme phosphorylase. This pathway acts as a "cascade" in that the product in each step is a catalyst for the next step, resulting in an amplification of the signal. Page Points 1 ____ 2 ____ 3 ____ 4 ____ Total ______ (8) (a) Diagram this signaling pathway for liver, indicating all the intermediate steps and intermediates from the first interaction of the hormone with the cell to the covalent modification of phosphorylase. (4) (b) What is the identity of the "second messenger" in this scheme (draw its structure), identify the protein it activates, and describe how it interacts with that protein. (6) (c) Name three other enzymes in liver whose activities are affected by covalent modification stimulated directly or indirectly by this second messenger. For each, indicate whether each enzyme is activatedor inhibited.
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