Sugar compounds include monosaccharides, polymers and derivatives of monosaccharides. Monosaccharide is polyhydroxy aldehyde or polyhydroxy ketone and their cyclic hemiacetal or derivative, aldehyde or ketone with multiple hydroxyl groups. Polysaccharides are polymers of monosaccharide condensation. Glucose is a monosaccharide. Maltose, sucrose and lactose are disaccharides.
Monosaccharide is the simplest kind of carbohydrate, and its molecule contains many hydrophilic groups, which are easily soluble in water and insoluble in organic solvents such as ether and acetone. Glucose is the main energy substance of life activities, ribose is the component of RNA, and deoxyribose is the component of DNA. There are many monosaccharides in organisms, such as ribose and deoxyribose, which contain 5 carbon atoms, and glucose, fructose and galactose, which contain 6 carbon atoms.
A sugar consisting of two monosaccharides linked together is called disaccharide. Disaccharide is formed by the dehydration of two monosaccharide units to form a valence bond called glycosidic bond. During dehydration, one molecule of monosaccharide removes hydrogen atoms, while the other molecule removes hydroxyl groups. The chemical formula of unmodified disaccharide can be expressed as c12h2o11. Although disaccharides are various, most of them are not common. Maltose, sucrose and lactose are common disaccharides. 1 molecule maltose is hydrolyzed to produce 2 molecules of glucose; 1 molecular sucrose hydrolysis produces 1 molecular glucose and 1 molecular fructose; 1 molecular lactose hydrolysis produces 1 molecular glucose and 1 molecular galactose. It can be seen that disaccharide is composed of two molecules of monosaccharide.
Polysaccharide? Include starch, cellulose, glycogen and xylose.