Classification of carbohydrates, meaning and general information about them.

Carbohydrates are organic compounds, which often contain three chemical elements: Carbon, Hydrogen and Oxygen. Many carbohydrates besides these elements contain Phosphorus, Sulfur and Nitrogen. These biopolymers are widely distributed in nature. The biosynthesis of carbohydrates in plants is realized as a result of photosynthesis. Carbohydrates account for about 80-90% of the dry mass of plants.

In humans, the concentration of carbohydrates in terms of dry matter is about 2% per cent. Carbohydrates are the main source of chemical energy for the body. Splitting of carbohydrates is of particular importance for the functioning of certain organs. For example, individual organs meet their needs mainly by splitting glucose: the brain by 80%, the heart by 70-75%. Carbohydrates are deposited in body tissues in the form of reserve nutrients (glycogen). Some of them perform supporting functions (hyaluronic acid), participate in protective functions, delay the development of microbes (mucus), is the chemical basis for constructing molecules of biopolymers, constituents of macroergic compounds, etc.

Classification of carbohydrates.

All carbohydrates are divided into two large groups: monosaccharides (simple carbohydrates or monoses), polysaccharides (complex carbohydrates or polyols), which consist of several residues of monosaccharide molecules linked together.

Classification of carbohydrates: monosaccharides.

Monosaccharides containing an aldehyde group are called aldoses, and those that contain a ketone group are called ketoses. Simple carbohydrates include aldehyde and keto alcohols with a number of carbon atoms of at least three. According to the number of carbon atoms, monoza is divided into trioses, tetrozes, pentoses, hexoses, etc.

The trioses. Contained in tissues and biological fluids in the form of esters of orthophosphoric acid as products of intermediate metabolism of carbohydrates during the reactions of glycolysis and fermentation. Tetrose. The most important is erythrose, which is contained in tissues in the form of an ester of orthophosphoric acid, a product of the pentose pathway for the oxidation of carbohydrates. Pentosises. Most pentoses are formed in the human digestive tract as a result of the hydrolysis of pentosans of vegetables and fruits. Part of the pentose is formed in the processes of intermediate metabolism, in particular in the pentose pathway. In tissues, pentoses are in a free state in the form of esters of orthophosphate acid, which are part of the macroergic compounds (ATP), nucleic acids, coenzymes (NADP, FAD) and other important bio-compounds. Of particular note are such pentoses: arabinose, ribose, deoxyribose, xylulose. Hexoses. They are found in a free state, in the composition of polysaccharides and other compounds. The most important representatives of this class of carbohydrates are glucose, fructose, galactose, manos.

Classification of carbohydrates: disaccharides.

Disaccharides are carbohydrates, the molecules of which under hydrolysis are split into two hexose molecules. Disaccharides include maltose, sucrose, trehalose, lactose.

When the name of disaccharides is usually used, names that have developed historically (lactose, maltose, sucrose), less often - rational and according to the nomenclature of IUPAC.

Disaccharides - solid crystalline substances, readily soluble in water, optically active, sweet to taste, capable of acid or enzymatic hydrolysis, can form esters.

Classification of carbohydrates: homopolysaccharides and heteropolysaccharides. The composition of homopolysaccharides includes a significant amount of residues of a single monosaccharide: glucose, manose, fructose, xylose, etc. They are reserve (reserve) nutrients for the body (glycogen, inulin, starch). The molecules of heteropolysaccharides consist of a large number of different monosaccharides.