. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Endocrine Mechanisms 757 Chapter 8). Glycogen is reversibly broken down to produce glucose-1-phos- phate under the influence of an enzyme phosphorylase, a process which has been referred to as phosphorolysis because of its similarity to hydrolysis. In phosphorolysis H3PO4 participates in the reaction in a manner comparable to that of H2O in hydrolysis. Under the influence of the enzyme phosphoglu- comutase the phosphate group is reversibly shifted within the molecule to the 6-position. The resulting glucose-6-ph
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. Endocrine Mechanisms 757 Chapter 8). Glycogen is reversibly broken down to produce glucose-1-phos- phate under the influence of an enzyme phosphorylase, a process which has been referred to as phosphorolysis because of its similarity to hydrolysis. In phosphorolysis H3PO4 participates in the reaction in a manner comparable to that of H2O in hydrolysis. Under the influence of the enzyme phosphoglu- comutase the phosphate group is reversibly shifted within the molecule to the 6-position. The resulting glucose-6-phosphate is reversibly split by the action of phosphatase to yield glucose and inorganic phosphate. Glucose-6- phosphate and fructose-6-phosphate, with which the former comes into equi- librium under the influence of the enzyme isomerase, comprise the primary substrates in the aerobic and anaerobic energy-yielding oxidative metabol- ism of carbohydrates. A number of endocrine glands in the mammal are known to influence the intermediary metabolism of carbohydrates and consequently the carbo- hydrate contents of body tissues. Adrenin, from the adrenal medulla, ele- vates blood sugar by accelerating the formation of lactic acid from glycogen in muscle and of glucose from glycogen in the liver. In muscle, after adren- MUSCLE. LIVER. Gluco^en Glucose Lactic Qc'id BLOOD Fig. 286. Diagram representing the gross metabolic transformations of carbohydrate in muscle and liver occurring in the higher vertebrate. alin administration, hexose monophosphate increases and inorganic phos- phate decreases. It would appear that adrenalin increases phosphorylase ac- tivity, since this is the predominant reaction common to both muscle and liver in these changes. Adrenalin accelerates this reaction only in living cells, being ineffective in enzyme solutions. Insulin from the islets of Langerhans of the pancreas appears to affect carbohydrate metabolism primarily through acceleration of the change, glu
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