Carbohydrates are organic compounds that often include three chemical elements: Carbon, Hydrogen and Oxygen. Many carbohydrates besides these elements contain Phosphorus, Sulfur and Nitrogen. These biopolymers are widespread in nature. The biosynthesis of carbohydrates in plants is carried out as a result of photosynthesis. Carbohydrates make up about 80-90% of the dry weight of plants.
In the human body, the concentration of carbohydrates in terms of dry matter is about 2% percent. Carbohydrates are the main source of chemical energy for the body. The breakdown of carbohydrates is of particular importance for the functioning of certain organs. For example, individual organs satisfy their needs mainly due to the breakdown of glucose: the brain - by 80%, the heart - by 70 - 75%. Carbohydrates are deposited in the tissues of the body in the form of reserve nutrients (glycogen). Some of them perform supporting functions (hyaluronic acid), participate in protective functions, inhibit the development of microbes (mucus), is the chemical basis for building biopolymer molecules, components of macroergic compounds, etc.
Classification of carbohydrates.
All carbohydrates are divided into two large groups: monosaccharides (simple carbohydrates or monoses), polysaccharides (complex carbohydrates or polyoses), which consist of several residues of monosaccharide molecules linked together.
Carbohydrate Classification: 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 at least three carbon atoms. According to the number of carbon atoms, monoses are divided into trioses, tetroses, pentoses, hexoses, etc.
Trioses. They are contained in tissues and biological fluids in the form of phosphoric acid esters as products of the intermediate exchange of carbohydrates during glycolysis and fermentation reactions. Tetrosa. The most important is erythrosis, which is contained in tissues in the form of phosphoric acid ester - a product of the pentose pathway for the oxidation of carbohydrates. Pentoses. Most pentoses form in the human digestive tract as a result of the hydrolysis of pentosans from fruits and vegetables. A part of pentoses is formed in the processes of intermediate exchange, 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 macroergic compounds (ATP), nucleic acids, coenzymes (NADP, FAD) and other important bio compounds. Particularly noteworthy are such pentoses: arabinose, ribose, deoxyribose, xylulose. Hexoses. They are found in a free state, as part of polysaccharides and other compounds. The most important representatives of this class of carbohydrates are glucose, fructose, galactose, and manose.
Carbohydrate Classification: Disaccharides.
Disaccharides are carbohydrates whose molecules, when hydrolyzed, break down into two hexose molecules. Disaccharides include maltose, sucrose, trehalose, lactose.
When naming disaccharides, they usually use names that have developed historically (lactose, maltose, sucrose), less often - rational and according to the IUPAC nomenclature.
Disaccharides - solid crystalline substances, readily soluble in water, optically active, sweet in 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 one monosaccharide: glucose, manose, fructose, xylose, etc. They are reserve (reserve) nutrients for the body (glycogen, inulin, starch). Heteropolysaccharide molecules are composed of a large number of different monosaccharides.