MCB 354 Chapter Notes - Chapter ch 15: Glycogen Synthase, Homeostasis, Hexose
7 Oct 2018
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15. 4 the metabolism of glycogen in animals through "carbohydrate and lipid. Metabolism are integrated by hormonal and allosteric mechanisms" Excess glucose is converted to polymeric forms for storage - glycogen in vertebrates and microorganisms and starch in plants. In vertebrates, glycogen is usually found in liver and skeletal muscle. Glycogen in muscle is there to provide a quick source of energy for either aerobic/anaerobic metabolism. Glycogenolysis = catabolic pathway from glycogen to glucose-6-phosphate. Gluconeogenesis = anabolic pathway from pyruvate to glucose. Glycogen breakdown is catalyzed by glycogen phosphorylase. Glycogen phosphorylase acts repetitively on the nonreducing ends of glycogen branches until it reaches a point four glucose residues away from a branch point, where its action stops. A debranching enzyme (oligo glucantransferase) further degrades by glycogen phosphorylase and it catalyzes two successive reactions that transfer branches. Glucose 1-phosphate can enter glycolysis or (in liver) replenish blood glucose.
