Carbohydrates

Carbohydrates are among the most widely distributed compounds in both plant and animal kingdoms. Plants can build up carbohydrates from carbon dioxide by photosynthesis. Many plants and animals contain large quantities of carbohydrates as reserve good material. Carbohydrates are also important structural components.
Carbohydrates (‘hydrates of carbon’) are so called because it was once thought that they could be expressed by the molecular formula Cx (H2O) y. Although this is true for a larger number of carbohydrates, some compounds like methyl pentoses and uronic acids do not conform to the formula, although they are regarded as carbohydrates.
Carbohydrates are aldehyde and ketone derivatives of polyhydroxy alcohols. Each carbohydrate therefore contains an aldehyde or a ketone group and is known as an aldose or a ketose.



In formaldehyde, a gas, R is replaced by hydrogen but the compound is not considered to be a carbohydrate although it has the empirical formula of a carbohydrate. Hydroxyacetaldehyde, a two-carbon compound, is also not considered to be a carbohydrate.
Carbohydrates are usually classified as monosaccharides, derived monosaccharides, oligosaccharides upon acid hydrolysis, while monosaccharide are stable to acid hydrolysis, while monosaccharide are stable to acid hydrolysis. There is no sharp distinction between oligosaccharides and polysaccharides, both being made up of monosaccharide units. The oligosaccharides, however, contain fewer monosaccharide residues than polysaccharides. The term polysaccharide is usually employed for polymers contain at least 10 monosaccharide units.

Types of Carbohydrates

1. Monosaccharides

2. Derived Monosaccharide

3. Oligosaccharides

4. Polysaccharides