Biochemistry

processes of the body. Thus, food is a source of not only plastic substances, but also energy. The main nutrients involved in the metabolism are proteins, fats and carbohydrates. An important role in the body is also played by the exchange of water, mineral salts and vitamins. All of them are closely interconnected and constitute a single whole (only for the convenience of studying the metabolism of each of the substances is considered separately). Through metabolism, carried out as a result of inextricably linked processes of assimilation and dissimilation, the body interacts with the environment, which is a prerequisite for life. The processes of assimilation and dissimilation are coordinated among themselves, organized in time and form an integrated system that ensures the preservation of a living organism, its normal functional ability. Complex system of regulatory mechanisms maintains the necessary level of intensity of the processes of assimilation and dissimilation according to the state of the body. Metabolism in tissues at the cellular and molecular levels occurs on the basis of self-regulation. In general, in the body, metabolism is regulated by the nervous and humoral (neurohumoral) pathways directly or through biologically active substances - hormones. Thyroxine, a hormone of the thyroid gland, which acting on the structure of mitochondria, increases the intensity of oxidative processes, has a great effect on metabolism. Thyroxine significantly affects protein metabolism. The adrenal hormone - adrenaline and pancreatic hormone - insulin, have a regulatory effect on carbohydrate metabolism. Hormones of the pancreas and thyroid gland, pituitary gland and adrenal glands participate in the regulation of fat metabolism. The speed of chemical metabolic reactions, their consistency and sequence are also regulated by enzyme systems. Metabolic programme. At different periods of a person ’ s life, metabolism has its own characteristics. At the age until 25 years, the processes of growth and development are not yet completed, the metabolism is characterized by a certain prevalence of assimilation over dissimilation. After 25 and up to 60 years in the metabolism equilibrium occurs. The intensity and volume of assimilation and dissimilation processes are approximately equal. By the age of 40, the “ protein ” program is gradually being replaced by a “ fat ” program, in which the formation of neutral fat is noted. In people aged 60 and over, the processes of dissimilation prevail over assimilation. 31