Carbohydrates

Carbohydrates form a very large group of naturally occurring organic compounds which play a vital role in daily life. They are produced in plants by the process of photosynthesis. The most common carbohydrates are glucose, fructose, sucrose, starch, and cellulose.

Chemically, the carbohydrates are defined as polyhydroxy aldehydes or ketones or substances which give such molecules on hydrolysis. Many carbohydrates are sweet in taste and all sweet carbohydrates are called as sugars.

Classification of Carbohydrates

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

Monosaccharides

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 among 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.

Disacccharides

Carbohydrates which give two monosaccharide molecules on hydrolysis are called disaccharides. For example, sucrose, maltose, and lactose.

Polysaccharides

Carbohydrates which yield a large number of monosaccharide units on hydrolysis. For example, starch, glycogen, and cellulose.