Submitted by: Nandeshori Devi Konthoujam

Vitamins are the complex organic substances found in various foods which are require for different metabolic reactions within the cells. Vitamins are required in small quantities for a variety of biochemical reactions and which generally can not be synthesize by the body and therefore must be supplied by the diet. The first discovered vitamins A and B which were found to be fat and water soluble vitamins respectively.

As more vitamins were discovered and shown to be either fat or water soluble vitamins thus it becomes the basis of classification of the vitamins. The water soluble vitamins are all designated members of the B complex apart from the vitamin C whereas the newly discovered fat soluble vitamins were given the designations as vitamin A,D, E, K. apart from their solubility characteristics t the water soluble vitamins have little in common from the chemical point of view.

Biochemical importance of water soluble vitamins is that the lack of these vitamins in diet leads to characteristic deficiency states and diseases. Diseases of a single vitamin of the B complex are rare, since poor diets are most often associated with multiple deficiency states. Nevertheless definite syndromes are characteristics of the deficiency of specific vitamins. Apart from vitamin C all water soluble vitamins are members of vitamin B complex and act as co factors of various enzymes in the body.

Thiamine (B1) is a cofactor in oxidative decarboxylation of ?-keto acids and of an important enzyme or the pentose phosphate pathway, transketolase. Riboflavin and niacin are each important co factors in the oxidation reduction reactions. Pantothenic acid is present in coenzyme A and acyl carrier protein, which act as carriers acyl groups in many important reactions. Biotin is the coenzyme xylase; the rate controlling enzyme in lipogenesis and pyruvate carboxylase, important for gluconeogenesis.

As well as having separate functions vitamin B12 and folic acid take part in providing one carbon residue for nucleic acid synthesis. Ascorbic acid is a water soluble antioxidant that maintains many metal co factors in the reduced state. Absence of water soluble vitamins from the diet provokes multiple deficiency states. Absence of a single vitamin leads to the characteristic deficiency syndromes.

Fat soluble vitamins have the common features of being a polar hydrophobic molecule and also of being isoprene derivatives. They all require normal fat absorption to be occurring for efficient absorption and if this mechanism is defective deficiency syndromes are likely to occur. Retinol and retinoic acid are considered to act in vision and has a role in glycoprotein synthesis. Vitamin D, a steroid prohormone is used in the regulation of calcium and phosphate metabolism and its omission from the diet leads to the rickets and osteomalacia.

Tocopherol or vitamin E is the most important antioxidant in the body acting in lipid phase of member target throughout the cell and protects against the effects if toxic radicals. Vitamin K is necessary for the synthesis several blood clotting factors like II, VII. IX, X and act as cofactor to carboxylase that cat on glutamate residues of blood clotting factor precursor proteins to enable them to chelate calcium.

About the Author: What are vitamins? Why we need take food containing vitamins? For detail information on the classification and the biomedical importance of different vitamins log on

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