Carbohydrates (Poly hydroxyaldehydes (or) ketones.)

Carbohydrates (Poly hydroxyaldehydes (or) ketones.)

A carbohydrate is composed of carbon, hydrogen and oxygen in the ratio of 1:2:1 (CH2O)n. They are of three types namely monosaccharides, disaccharides and polysaccharides

Monosaccharides:

These are the simplest form of carbohydrates being comprised of a single organic molecule. Depending on the number of carbon atoms they are classified into trioses, tetroses, pentoses, and hexoses.

The trioses (C3H6O3) are common intermediary products in carbohydrate metabolic processes. They play an important role in inter con version of biomolecules. (eg. glyceraldehydes). Pentoses (C5H10O5) like ribose and deoxyribose are the integral components of RNA and DNA molecules. The Hexoses(C6 H12O6) such as glucose, fructose and galactose are food components commonly consumed.

Carbohydrates are commonly employed by the cells for providing energy. The energy metabolism happens through glycolytic processes involving oxidative, citric acid cycle. The energy liberated is stored in the form of ATPs (Adenosine triphosphate).

Each gram of carbohydrate is capable of yeilding energy equivalent of 4.1 calories.

Disaccharides

These are the carbohydrates formed by condensation of two monosaccharide monomers. These are found in common food substances such as milk and sugar. There are three common disaccharides namely mal-tose, sucrose and lactose. They have the following composition

Maltose(In germinating cereals)            � glucose + glucose

Sucrose (cane sugar)                              � glucose + fructose

Lactose (milk)                                         � glucose + galactose

Polysaccharides

These are complex carbohydrates formed by polymerisation of a large number of monosaccharides. Nature abundantly produces various types of polysaccharides. Several of them are structural components in the living world eg. chitin, cellulose. Starch molecules serve as storage food materials trap-ping enormous amount of energy. In food grains, starch is available as pectin and amylopectin molecules. Glycogen, a polysaccharide is found in liver and muscles.