Biochemistry

using its tissue cells, i.e. it increases the permeability of cell membranes to glucose, which leads to a decrease in its content in the blood (hypoglycemic effect). Glucose entering the cells with the participation of ATP and hexokinase is converted into glucose-6-phosphate. The resulting glucose-6-phosphate cannot leave the cell and undergoes various transformations. With an excess of glucose in the cells, insulin stimulates the synthesis of glycogen in the liver and muscles, the oxidation of monosaccharides and their conversion into lipids. With insulin deficiency, an increase in blood glucose levels (hyperglycemia), excess glucose excretion in the urine (glycosuria) and a decrease in the amount of glycogen in the liver are observed. Persistent hyperglycemia and glycosuria are symptoms of diabetes mellitus - a serious illness, caused in most cases by a violation of the insulin-forming function of the pancreas. A temporary increase of the amount of glucose in the blood and its appearance in the urine is called, respectively, alimentary (food) hyperglycemia and glycosuria. They occur when high consumption of sweet carbohydrates (over 100 g at a time). One of the other important hormones is adrenal - adrenal medulla hormone. It causes hyperglycemia, as it activates the liver enzyme phosphorylase, which catalyzes the breakdown of glycogen contained in it to free glucose. The mechanism of action of adrenaline is complex. In the liver, it activates the conversion of an inactive form of phosphorylase into an active one through a series of intermediate transmitters (cell receptors, adenylatecyclase, c-AMP, protein kinase, etc.). In muscles, adrenaline activates the breakdown of glucose to lactic acid. The а -cell hormoneof the islets of Langerhans of the pancreas participates in the regulation of carbohydrate metabolism and glucagon. The hormones of the adrenal cortex- glucocorticoids, affect the blood glucose level. They increase its level by activating the production of glucose from non ­ carbohydrate components (gluconeogenesis). Pituitary hormones (adrenocorticotropic, somatotropic, etc.) stimulate the production of glucocorticoids and, consequently, forward to an increase in blood glucose level. A special role in the regulation of carbohydrate metabolism belongs to the liver. It actively proceeds with the breakdown and synthesis of glycogen. When hypoglycemia occurs, the active breakdown of liver glycogen to glucose, which then enters the blood, happens. During hyperglycemia liver cells actively capture glucose from the blood and use it to synthesize glycogen. The participation of the liver in the regulation of carbohydrate metabolism is manifested in the inactivation of glucocorticoids and in the inhibition of the synthesis of insulinase, an enzyme that breaks down insulin. In addition, there is another way of regulation - 214