Question

Outline the process of Gluconegenesis and Glycogen metabolism and compare and contrast between them.

Answer 1

Glycogenolysis is the biochemical breakdown of glycogen to glucose whereas glycogenesis is the opposite, the formation of glycogen from glucose. Glycogenolysis takes place in the cells of muscle and liver tissues in response to hormonal and neural signals. In particular, glycogenolysis plays an important role in the adrenaline-induced fight-or-flight response and the regulation of glucose levels in the blood. The reverse process, glycogenesis, the formation of glycogen from glucose, occurs in liver and muscle cells when glucose and ATP are present in relatively high amounts. In the synthesis of glycogen, one ATP is required for every glucose unit incorporated into the polymeric branched structure of glycogen. The glucose (in the form of glucose-6-phosphate) is synthesized directly from glucose or as the end product of gluconeogenesis.

Glycogen is a multi-branched polysaccharide of glucose that serves as an energy store primarily in muscle and liver. It is stored in the form of granules in the cytoplasm of the cell and is the main storage form of glucose in the body. The concentration of glycogen in muscle is low (1-2% fresh weight) compared to the levels stored in the liver (up to 8% fresh weight).Glycogen is an energy reserve that can be quickly mobilized to meet a sudden need for glucose. The significance of the multi-branched structure is that multiple glucose units, rather than a single glucose can be mobilized from any glycogen molecule when glycogenolysis is initiated.