Biochemistry

CHAPTER 7. CHEMISTRY OF CARBOHYDRATES 7.1 BIOLOGICAL ROLE, STRUCTURE, PROPERTIES OF CARBOHYDRATES AND THEIR DERIVATIVES Carbohydrates are biochemical compounds formed in plants as primary products of photosynthesis . Their name comes from the general formula of this group of substances - C n (H 2 O) n , which includes carbon, hydrogen and oxygen (the ratio of hydrogen and oxygen atoms in them is the same as in water). The term “ carbohydrates ” was first proposed by the professor of the University of Dorpat (Tartu) K.Schmidt in 1844. It turned out, however, that the composition of not all carbohydrates corresponds to the above formula, in connection with which the International Commission for the Reform of Chemical Nomenclature proposed the term “ carbohydrates ” to be replaced by “ glycides ” . Nevertheless, it was not widely used and the name “ carbohydrates ” remained universally recognized. In plants, carbohydrates make up 80-90% of the mass, and their content varies in different parts. So, in green parts of plants it makes up 2.5 -6%, in potato tubers and root crops - 10-20%, in cereal grains - up to 70%. In the body of humans and animals, carbohydrates are present in lesser amounts than proteins and lipids, and make up only 2% of the dry matter mass. However, for humans, their value is very great. This is evidenced by the diverse functions that carbohydrates perform. Energy function. Carbohydrates 60% provide the body with energy. During the oxidation of 1 g of carbohydrates, about 4 kcal of energy is released. Plastic function. Carbohydrates take part in the synthesis of many substances necessary for the life of the body, such as nucleoproteins, lipoids, complex enzymes, mucopolysaccharides, etc. The function of nutrients. Carbohydrates have the ability to be stored in the body in the form of glycogen, a storage carbohydrate that is consumed as needed. Glycogen is mainly concentrated in the liver and muscles. With proper nutrition, up to 10% of glycogen by weight of the liver can accumulate in the liver, and up to 2% in the muscles. When fasting, glycogen stores are reduced to 0.2%. Protective function. Viscous secrets (mucus) secreted by various glands are rich in mucopolysaccharides . They protect the walls of hollow organs from mechanical damage, from the penetration of pathogenic bacteria and viruses. 134