Disaccharides: -
Disaccharides defined can be as a second-degree complex
carbohydrate compounds which are produces by formed by the attachment of two
monosaccharide molecules by glycosidic linkage. Same as monosaccharides, disaccharides
are also soluble in water. Some common examples of disaccharides are the
Sucrose, Lactose, Maltose. The joining of the double sugar into a double sugar
compound happens by the action of condensation reaction where the elimination
of water molecules from the functional groups takes place. Breaking down a double
sugar into its simplest sugar forms by the process of hydrolysis by the help of
the enzyme disaccharidase.
Disaccharides can
be classified into two functionally different classes: -
1. Reducing Disaccharides/ Reducing Sugars.
2. Non-Reducing Disaccharides/ Non-Reducing sugars.
Reducing sugar: -
A monosaccharide
of the paired disaccharide, in which the reducing sugar has one free hemiacetal
unit that can function as a reducing aldehyde group or a reducing ketone group.
Examples of reducing sugars are the cellobiose and maltose, having a one free
hemiacetal unit to function as a reducing aldehyde group and the other occupied
by the glycosidic bond, preventing it from acting as a reducing sugar.
Non-Reducing sugar: -
Are those in which
the component monosaccharides bond through acetal linkage between their anomeric
carbons, this left a monosaccharide with no left out free hemiacetal unit to
act as a reducing unit. Sucrose and Trehalosa are non-reducing sugars because their
glycosidic bond are between their respective hemiacetal carbon atoms. The
reduced activity of non-reducing sugars in comparison to reducing sugars, may
be an advantage where stability in storage is important.
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