Water is an integral part of cell tissue. Most of the water in organisms combines with protein to form colloid, which makes tissues and cells have certain morphology, hardness and elasticity. Water is an important part of cell colloid protoplasm. Without water, the colloidal state of cells cannot be maintained and various metabolism cannot be carried out.

(b) participation in substance metabolism

Water is the main solvent for metabolites in organisms. Water has high electrolysis constant and strong solubility. The absorption and transportation of nutrients and the elimination of metabolites in many feeds are inseparable from the participation of boiling water. Because the exchange and transfer of nutrients and metabolites and the transportation of various active substances (enzymes, hormones and vitamins) can only be carried out in the body if they are dissolved or dispersed in body fluids.

(3) promoting biochemical reaction

Water is a substance that promotes metabolic reactions, and all biological oxidation and enzymatic reactions involve water. Water is not only the raw material in organism, but also the product of biochemical reaction. In the process of hydrolysis, water is the reaction substrate; In the process of oxidation, water is the product of reaction. Water participates in digestion, absorption, decomposition, synthesis, redox and cell respiration in the body.

(4) Maintain the balance of body fluids

Water is an important substance to maintain the balance of body fluids. Body fluid refers to the liquid composed of water and various substances (such as inorganic salts, glucose, amino acids, protein, etc.) existing in animals. ) Soluble in water. It exists widely inside and outside cells and constitutes the internal environment of animals. Water can dilute the contents of cells and body fluids, make substances move relatively freely in cells, body fluids and digestive tract, maintain the ion balance of minerals in the body, and maintain the normal metabolism of substances in the body. Water not only plays an important role in expelling a large number of indigestible substances in the digestive tract, but also plays an important role in expelling metabolites through urine and sweat.