From Big Medical Encyclopedia

ENERGY (Greek energeia action, activity) — the general quantitative measure of the movement and interaction of all types of matter. AA. does not arise disappears from nothing, it can only pass from one form into another. One of the most fundamental laws of nature — the law of energy conservation — says: in the isolated system

energy remains (see Thermodynamics). The concept «energy» connects together all natural phenomena.

According to various forms of motion of matter consider different forms E.: kinetic, mechanical, potential, chemical, nuclear, etc. The motive energy (W) of a moving particle is defined by its weight (m) and mV2

the speed (V): W = - at - * Such particle can make mechanical work (A), at the same time its energy will decrease: And = W2 — Wx. In the field of gravity mechanical work can be made due to change of a potential energy, edges near Earth mgh where m — body weight, is equal to g — acceleration of gravity, h — height over the Earth's surface. A potential energy of a particle with a charge of q is equal in electric field to qcp where f — electric potential in this point of electric field. Full E. any body it consists of its motive and potential energy (as whole) and an internal energy, edge represents the sum of all types of energy of particles taking into account their interactions in this body. A part of an internal energy (so-called free energy) can be spent for commission of mechanical work. In live organisms chemical

E., concluded in food stuffs and oxygen of air, partially passing a thermal form E., it is spent for commission mechanical, electric and osmotic (see. Osmotic pressure) works, i.e. on movement of bodies and molecules against mechanical, electric and osmotic forces, and also on maintenance of constant body temperature at advanced animals.

Transformation E. in living cells (see Bio-energetics) includes processes of its storage in the form of you-sokoergichesky connections (see) and its expense on power needs of an organism: transfer of ions against

a gradient (see) concentration (see Transport of ions) through biol. membranes (see Membranes biological), digestion (see), transfer of nervous impulse (see. A nervous cell), synthesis of all main substances in a cell (see the Metabolism and energy), muscular contraction (see), the movement of fibers, flagellums, etc. Synthesis of the main accumulator of energy — ATP (see Adenozinfosforny acids) in cells of plants is provided due to conversion of energy of light and photosynthetic phosphorylation (see Photosynthesis), and at animals and the person is carried out generally as a result of cellular respiration — biol. oxidation and oxidizing phosphorylation (see biological oxidation). In the beginning an internal energy of organic molecules, e.g. carbohydrates (see), allocated during the redoxreactions (see) proceeding in mitochondrions (see) and other power interfacing membrane structures, turns into a form of a difference of electrochemical potentials on both sides biol. membranes (Dts, N +) as a result of transfer of protons (ions of H+) interfaced to electron transfer in a respiratory chain. Then this energy is spent for synthesis of ATP, that is stocks up in the form of convertible chemical energy.

Important feature of systems of transformation E. in normally functioning cell almost full reversibility of all processes proceeding in it, i.e. high efficiency is. At development patol. processes, napr, at ischemia, physical overworks, a stress, intoxications, etc., the irreversible transition of a part of energy to its thermal form connected with dissociation of oxidizing phosphorylation and breath in mitochondrions as a result of disturbance of barrier function of membranes is observed. At the same time E. oxidations of organic substrates it is spent «empty», and cells can die from a lack of ATP, that is for power hunger.

Bibliography: Vladimirov Yu. And»

, etc. Biophysics, M., 1983; Remizov A. N. Course of physics, electronics and cybernetics, M., 1982; The Cheekbone -

h e in V. P. Transformation of energy in biomembranes, M., 1972.

Yu. A. Vladimirov.