Biochemistry

I но - с - н I н - с-он I н -с-он I сн,он (X-D- glucopyranose 0-D-glucopyranose (cyclic forms) D-glucose (acyclic form) Monosaccharides exist mainly in semi-acetal forms. Semi-acetal hydroxyl is highly reactive. In reactions with alcohol, carboxylic acids, phenols, it can be replaced by other groups. A compound that acts on the hemiacetal hydroxyl of a monosaccharide is called an aglycon, and the reaction product is called a glycoside. Glycosides are physiologically active substances, a- and 0-isomers of monosaccharides correspond to a- and 0-glycosides. O- glycosides are formed by reaction with alcohols and phenols (the bond is via oxygen); N- glycosides - a glycosidic bond is carried out through nitrogen with a radical of an organic compound that is not a carbohydrate. Glycosides play an important role in metabolism. They are the products of the cleavage of nucleic acids and nucleoproteins (nucleotides and nucleosides), ATP, NAD, NADP; These include some antibiotics, plant pigments, alkaloids, etc. H — C — OH COOH (acyclic form) D- glucuronic acid 136