Classification of Carbohydrates

Carbohydrates are classified into three groups depending upon their behavior on hydrolysis.

i. Monosaccharide’s:

A polyhydroxy aldehyde or ketone which cannot be hydrolyzed further to a smaller molecule containing these functional groups is known as a monosaccharide. About 20 monosaccharides occur in nature and glucose is the most common amongst them. Monosaccharides are further classified on the basis of the number of carbon atoms and the functional group present in them. If a monosaccharide contains an aldehyde group, it is known as an aldose and if it contains a keto group,it is known as a ketose. The number of carbon atoms present is also included while classifying the compound as is evident from the examples given in Table 1.

Glucose occurs freely in nature as well as in the combined form. It is present in sweet fruits and honey. Ripe grapes also contain glucose in large amounts.

ii. Disaccharides:

Carbohydrates which give two monosaccharide molecules on hydrolysis are called disaccharides e.g. sucrose, maltose, lactose etc.

iii. Polysaccharides:

Carbohydrates which yield a large number of monosaccharide units on hydrolysis e.g. starch, glycogen, cellulose etc