The organism in the course of activity feels the constant need for nutrients. Various food in the course of digestion turn into amino acids, monosugar, glycine and fatty acids. These simple substances are soaked up and carried by blood on all organism.
Before becoming nutrients, usual daily food – rough, tasty, useful, exotic – undergoes preparatory processing. The route of passing and gradual transformation of food is called digestive tract. It includes a mouth where food, being exposed to crushing, mixes up with saliva and turns into a food lump. Through a gullet with his own numerous glands, food gets into a stomach. The mucous membrane of a stomach contains glands producing slime, enzymes and hydrochloric acid. The food processed by gastric juice comes to a small intestine. Having undergone necessary physical and chemical treatment in digestive tract, nutrients in the form of the simplest molecules are soaked up through a mucous membrane of intestines. Then blood transfers them to cells of various fabrics. In organism cages constantly there is a process of a metabolism. Or metabolism. It is a set of various chemical reactions which proceed in a living organism for its functioning and growth. Metabolism is subdivided into two stages: catabolism and anabolism. Catabolism is called process of degradation of complex organic matter to simpler. Anabolism – process at which the main substances of our organism are synthesized: proteins, sugar, lipids, nucleinic acids. At the same time the organism spends a certain amount of energy. The metabolism is carried out between fabric of a cage and intercellular liquid. Constancy of composition of intercellular liquid just is also maintained by blood current. In the course of blood circulation during passing through walls of capillaries plasma of blood is updated 40 times, exchanging with interstitial liquid. Both anabolism, and catabolism are closely interconnected on time and in space and are essentially identical at all species of microorganisms, plants and animals.