Biochemistry

CHAPTER 13. REGULATION OF EXCHANGE OF SUBSTANCES IN ORGANISM 13.1. GENERAL REPRESENTATIONS ON THE REGULATION OF SUBSTANCE EXCHANGE The life essence of any organism is on exchange of substances and energy. Living organisms are characterized by a high degree of orderliness of metabolism, representing complex targeted regulatory systems. Metabolism and energy is a natural order of transformation of substances and energy in living systems, aimed at their conservation and self-reproduction. Whole set of chemical reactions that occur in living organisms, including an assimilation of substances from the outside (assimilation), and their cleavage (dissimilation) up to the formation of final products to be removed from the body, is the essence of this process. In each cell of organs and tissues, thousands of chemical reactions take place simultaneously, closely related to each other in space and time. Protein bodies play a dominant role in this endless array of interactions. Thanks to their catalytic function, a huge number of chemical processes of decay and synthesis are carried out. With the participation of nucleic acids, strict specificity of the biosynthesis of macromolecules is maintained, and therefore, species specificity in the structure of the most important biopolymers is maintained. The exchange of carbohydrates and lipids is associated with the constant formation of reserves of ATP - a universal energy donor for chemical reactions. These same substances are the source of the simplest organic molecules from which biopolymers and other compounds are synthesized. As a result, a continuous process of self-renewal of living matter is carried out. General course of biochemical processes in the body is a single whole, and the body acts as a self- adjusting system that supports its own existence due to metabolism (Fig. 13.1). The main stages of metabolism are the consumption of nutrients, their digestion and absorption in the gastrointestinal tract, the transport of compounds to organs and tissues of the body, their entry into the structural formations of cells - organoids, where specific transformations and excretion of decay products occur. At each of these stages, certain regulatory mechanisms operate. The intake, digestion and absorption of nutrients in the digestive system are regulated at the level of the whole organism and organ systems. So, environmental factors (temperature, humidity, pressure, etc.) and nutrition through the central nervous system affect the metabolic processes of the whole organism. 275