The disaccharide that is constituted of two glucose units isA. sucroseB. lactoseC. maltoseD. cellobiose

The disaccharide that is constituted of two glucose units isA. sucrose

1.	The disaccharide that is constituted of two glucose units isA. sucroseB. lactoseC. maltoseD. cellobiose
Answer» Correct Answer - D Disaccharide, maltose is composed of two `alpha-D-` glucose units in which `C1` is of one glucose is linked to `C4` of another glucose unit. In solution, the free aldehyde group can be produced at `C1` of second glucose in solution, hence maltose shows reducing properties. Partial hydrolysis of cellulose (cotton fibres) gives the disaccharise cellobiose, `C_(12) H_(22) O_(11)`, which resembles maltose in every respect except one: configuration of its glycosidic linkage. Cellobiose, like maltose, is a reducing sugur, forms an osazone, exists in alpha and beta forms that undergo mutarotation and on acid-catalyzed hydrolysis, yields two molar equivalents of `D-(+)-` glucose. The sequence of oxidation (with `Br_(2)//H_(2) O)`, methylation (with `Me_(2) SO_(4), NaOH)` and hydrolysis `(H_(2) O, H^(+))` shows that `C1` of one glucose unit is connected in glycosidic linkage with `C4` of the other and that both rings are six membered. `(+)-` Cellobiose differs from `(+)-` maltose in one respect: it is hydrolyzed by the enzyme emulsin (from bitter almonds), not by maltose, Since emulsion is known to hydrolyze only `beta`-glucoside linkages, we can conclude that the structue of `(+)-` cellobiose differs from that of `(+)-` maltose in only one resect: the D-glucose units are joined by a beta linkage rather than by an alpha linkage.