Go Metabolism and energy in the human body metabolism anabolism catabolism

Metabolism and energy

Metabolism and energy ( metabolism ) are the transformations of substances and energy that underlie the vital activity of organisms. Receiving from the environment a variety of organic and inorganic substances (mainly food), the body absorbs them, that is, processes them into substances specific to itself. This side of metabolism and energy is referred to as assimilation.

The process of destruction of organic substances - dissimilation - is the opposite side of the assimilation of metabolism and energy. Assimilation and dissimilation are inextricably linked with each other. Growth, development, reproduction are always characterized by the predominance of assimilation, which is manifested in an increase in the total mass of the body, in the formation of new tissues and organs, in their growth and degree of differentiation. In some pathological conditions, as well as during starvation, dissimilation prevails, which is usually expressed in a decrease in the mass of the living body.

The intensity of metabolism and energy in general depends on the relationship of the organism with the environment. In higher animals and humans, metabolic and energy processes, including the ratio of assimilation and dissimilation, are regulated by the central nervous system.

The concept of metabolism and energy includes both the processing of nutrients by the body and the transformation of those substances that are part of the body.


The processes of transformation of substances in tissues and organs, including the formation and splitting of intermediate products, are called interstitial metabolism. The study of interstitial metabolism gives an idea about the sequence of biochemical transformations inside the body, about their localization in certain organs and tissues, about the interrelation of various chemical reactions in a single process of metabolism and energy of the whole organism.

Metabolism and energy are divided into anabolic and catabolic. The term "anabolism" refers to those chemical reactions in which simpler substances, interacting with each other, form more complex ones, which leads to the construction of a new protoplasm of cells, to the overall growth of a living organism. Anabolic processes underlie assimilation, catabolic processes are at the basis of dissimilation. Catabolism is the splitting of organic substances not only food, but also tissue, which leads to the expenditure of cell protoplasm. Anabolic and catabolic processes are continuous, being in a complex dynamic relationship; they can not be separated from each other. Substances resulting from catabolic processes are not only excreted from the body in the form of end products of metabolism, but can also be involved in anabolic processes: complex compounds are split, and their components, combined in various combinations, form new substances. Thus, the synthesis of tissue proteins, fats and carbohydrates is preceded by the breakdown of dietary proteins, fats and carbohydrates (see Nitrogen metabolism, Fat metabolism, Carbohydrate metabolism ).

The most important function of catabolism is the release of energy contained in organic compounds entering the body or deposited in it as a reserve substance. Energy is used to renew and restructure tissues; consumed in the functioning of organs (for example, muscular work, transmission of nerve impulses, etc.); spent in the synthesis of organic compounds, including enzymes ; part of it is released in the form of heat.


Catabolic processes that produce energy are fermentation in plants and microorganisms, glycolysis in animals, or oxidation of organic substances to CO 2 and H 2 O, which is common in both animal and plant tissues. If carbohydrates are subjected to oxidation, then at the absorption of 1 l of oxygen 5.05 kcal of energy is released, if fats and proteins, respectively 4.7 and 4.8 kcal. Each of these substances corresponds to a certain value of the respiratory coefficient (Rq), that is, the ratio of the volume of CO 2 released during a given period of time to the volume of oxygen absorbed by the body during this time interval. In the oxidation of carbohydrates, Rq is equal to 1, fat - 0.7, protein - 0.8. Since the splitting of various nutrients in the body occurs simultaneously, the value of Rq can vary. The average value of Rq for a person is normally in the range of 0.83– 0.87. Having determined Rq experimentally, with the help of special tables, the amount of energy released in calories is set. Energy exchange, thus, can serve as an indicator of the intensity of metabolic processes in the body and is characterized by the value of the balance (total) exchange.

In clinical practice, to compare the intensity of metabolism and energy in different people and identify its deviations from the norm, they initially determine the level of basal metabolism, i.e., the amount of energy used only to maintain life at rest, on an empty stomach, which is characterized by the same organism of considerable constancy.

Based on the numerous definitions of basic metabolism in humans, tables of normal values ​​of this indicator were compiled depending on age, sex, and total body surface. In these tables, the basal metabolism values ​​are given in large calories (kcal) per 1 m 2 of body surface for 1 hour. In individuals of the same sex, height, weight and age, basal metabolism is approximately the same and varies within ± 10–15%. Environmental factors (climate, temperature, barometric pressure), various forms of work activity, sports , the mode and type of food, the functional state of the body cause quite significant deviations from the norm. Changes in the hormonal function of the body have a major effect on basal metabolism. The action of the thyroid gland is especially pronounced: with its hyperfunction, the basal metabolic rate may exceed the normal level by 80%, with hypofunction, the basal metabolism may be below the norm by 40%. Loss of function of the anterior lobe of the pituitary or adrenal cortex leads to a decrease in basal metabolism. The excitation of the sympathetic nervous system, enhanced education or the introduction of adrenaline from the outside reinforce the basal metabolism. In the clinic, the study of basic metabolism is carried out on an empty stomach, i.e. in 12-16 hours. after eating, determining the gas exchange for 10-15 minutes Room temperature - from 20 to 22 °. The basal metabolic rate is usually given as a percentage of deviations from the norm.

See also Biological oxidation.