Glycogen breakdown

The energy stored in the a(l 4) glycosidic bond during the condensation reaction in glycogen synthesis is sufficient to permit the formation of a glucose-phosphate bond without using ATP. 

CHAPTER 15 Carbohydrate Metabolism II Gluconeogenesis, Glycogen Synthesis and Breakdown, and Alternative Pathways 

Glucose-1-phosphate is next converted by phosphoglu-comutase to glucose-6-phosphate. The latter may then enter the glycolytic pathway, but if glucose-6-phosphatase is present, free glucose can be formed. 

Glycogen phosphorylase sequentially removes the glu-cosyl residues from a glycogen branch until further action is sterically hindered by a branch point. This occurs when the branch is four residues long from the branch point. Debranching enzyme, a multifunctional protein, first removes the trisaccharide stump on the branch and then removes the branch point itself. The a(l 4) glycosidic bond link- 

---

Physiological response glycogen breakdown visual excitation histamine secretion in all allergic reactions slowing of pacemaker activity that controls the rate of the heartbeat... 

Stimulation of glycogen breakdown involves consumption of molecules of ATP at three different steps in the hormone-sensitive adenylyl cyclase cascade (Figure 15.19). Note that the cascade mechanism is a means of chemical amplification, because the binding of just a few molecules of epinephrine or glucagon results in the synthesis of many molecules of cyclic / MP, which, through the action of c/ MP-dependent protein kinase, can activate many more molecules of phosphorylase kinase and even more molecules of phosphorylase. For example, an extracellular level of 10 to 10 M epinephrine prompts the for-... 

Glucagon Gs-cAMP-A kinase glycogen breakdown (muscle), gluconeogenesis (liver)... 

The glycolytic pathway and those for glycogen breakdown and synthesis are shown in Appendix 2. 

Integration of regulation of glycogen synthesis and glycogen breakdown by glucose... 

A decrease in the activity of phosphorylase, so that glycogen breakdown is decreased. 

Glycogen synthesis in liver and muscle Glycogen breakdown in liver Fat synthesis in liver Fat breakdown in adipose tissue Protein synthesis in muscle Protein breakdown in muscle... 

---