Metabolism. Biological sense Metabolism - a set of changes and interconversion of chemical elements and compounds. Simultaneously, there is two opposing processes. Assimilation: the formation of complex organic substances t.e.belkov, fats, carbohydrates, and nucleic acids. Assimilation is always accompanied by the absorption of energy. And dissimilation: the decay of substances.Dissimilation is always accompanied by the release of energy. Metabolism and energy exchange occur simultaneously. The potential energy introduced into the body of chemical compounds is converted into heat and is spent on maintaining a constant body temperature and the mechanical in the process. The body needs a constant metabolism and this constancy is ensured receipt of food. Incoming nutrients make up for the loss of organic matter, occurring as a result of dissimilation and the body thus receives a building material for growth and renewal of old cells. Nutrients - is a source of energy for the life of the organism. Absorption of nutrients by the body only after they are converted (split) into simpler and readily soluble substances. In the process of splitting a large role played by digestive enzymes. Important role in metabolism is water. And also with a variety of minerals and vitamins. Through continuous metabolism (metabolism), supported by life itself, remains constant chemical composition and physico-chemical properties of the internal environment of the body: the body temperature constant, kilotno-base balance, and other parameters. To refer to the totality of the internal environment of the body adopted the term "homeostasis." It provides the body relative independence from the environment in which the constantly changing conditions. Nezavisimot not complete, and the relative t.k.organizm need water, oxygen, nutrients from the environment. Independence from the environment provided by the nervous, endocrine and circulatory systems. The immune system provides resistance to the action of microorganisms, harmful physical and chemical agents. Termorgulyatsii system creates independence from temperature changes. Body is designed so well that every time adapts to any external influences, while remaining otnoitelno nezavisymym.