Problem 1
What are the three steps in glycogen degradation, and what enzymes catalyze each step?
Problem 2
Match each term with its description. (a) Glycogen phosphorylase__________ (b) Phosphorolysis_____________ (c) Transferase_____________________ (d) \(\alpha-1,6-\) Glucosidase____________________ (e) Phosphoglucomutase____________________ (f) Phosphorylase kinase______________ (g) Protein kinase \(\mathrm{A}\)______________ (h) Calmodulin______________ (i) Epinephrine______________________ (j) Glucagon______________ 1\. Calcium-binding subunit of phosphorylase kinase 2\. Activates glycogen phosphorylase 3\. Removal of a glucose residue by the addition of phosphate 4\. Stimulates glycogen breakdown in muscle 5\. Liberates a free glucose residue 6\. Shifts the location of several glucose residues 7\. Stimulates glycogen breakdown in the liver 8\. Catalyzes phosphorolytic cleavage 9\. Prepares glucose 1-phosphate for glycolysis 10\. Phosphorylates phosphorylase kinase
Problem 6
Hers disease results from an absence of liver glycogen phosphorylase and may result in serious illness. In McArdle disease, muscle glycogen phosphorylase is absent. Although exercise is difficult for patients suffering from McArdle disease, the disease is rarely life threatening. (a) Account for the different manifestations of the absence of glycogen phosphorylase in the two tissues. (b) What does the existence of these two different diseases indicate about the genetic nature of the phosphorylase?
Problem 8
What is the biochemical rationale for the inhibition of muscle glycogen phosphorylase by glucose 6 -phosphate when glucose 1 -phosphate is the product of the phosphorylase reaction?
Problem 9
What is the predominant form of glycogen phosphorylase in resting muscle? Immediately after exercise begins, this form is activated. How does this activation take place?
Problem 10
Outline the signal transduction cascade for glycogen degradation in muscle.
Problem 11
What path in addition to the cAMPinduced signal transduction is used in the liver to maximize glycogen breakdown?
Problem 12
There must be a way to shut down glycogen breakdown quickly to prevent the wasteful depletion of glycogen after energy needs have been met. What mechanisms are employed to turn off glycogen breakdown?
Problem 13
Glycogen is not as reduced as fatty acids are and consequently not as energy rich. Why do animals store any energy as glycogen? Why not convert all excess fuel into fatty acids?
Problem 14
Glycogen depletion resulting from intense, extensive exercise can lead to exhaustion and the inability to continue exercising. Some people also experience dizziness, an inability to concentrate, and a loss of muscle control. Account for these symptoms.
