Disaccharides contain two sugar units linked through glycosidic bonds. Sucrose is the commercial sugar, which has little importance in the functions of the cell. However, lactose, a disaccharides of mammalian origin is a product of milk secreting glands. Disaccharides generally occur free in plants, but their physiological importance remains obscure.
Maltose is a disaccharide that is obtained from partial hydrolysis of starch. It is composed of two glucose residuces which are condensed together through glycosidic linkage. The Linkage exist between the hydroxyl group of C-1 of one residue and C- 4 of the next glucose molecule. The linkage is known as α-1, 4 glycosidic linkage.

Cellobiose also contains two D – glucose residues, but the linkage in this case exists between the OH group of C-1 which is in beta position and the fourth carbon of the  next residue . The linkage is known as β-1,4,Glycosidic linkage.