Lesson 7 : Carbohydrates - Classification- Structure, Function


Two joined monosaccharides are called a disaccharide and these are the simplest polysaccharides. Examples include sucrose and lactose. They are composed of two monosaccharide units bound together by a covalent bond known as a glycosidic linkage formed via a dehydration reaction, resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other.

Sucrose, is the most abundant disaccharide, and the main form in which carbohydrates are transported in plants. It is composed of one D-glucose molecule and one D-fructose molecule

Lactose, a disaccharide composed of one D-galactose molecule and one D-glucose molecule, occurs naturally in mammalian milk. The systematic name for lactose is O-?-D-galactopyranosyl-(1?4)-D-glucopyranose. Other notable disaccharides include maltose (two D-glucoses linked ? -1, 4) and cellulobiose (two D-glucose linked ?-1, 4)

Last modified: Wednesday, 18 January 2012, 6:21 AM