Food Chemistry and Fish in Nutrition ( 2+1)

6.5.1.Introduction   

Oxidation is chemically defined as the removal of electrons and Reduction is the gain of electrons. The free oxidation takes place with the production of flames and much heat , while in the living organism oxidation takes place near room temperatures in aqueous solution or at lipoprotein surfaces, and the free energy of combustion is efficiently recovered and utilised. Substances like glucose or citric acid are stable indefinitely in the air are smoothly oxidised by living cells. The biological combustion is under the control of enzymic catalysis. An iron containing enzyme system( the cytochrome system) present in the tissues enables molecular oxygen to serve as an oxidixing agent.

The enzymes involved in biological oxidation–reduction are (1) dehydrogenases with carriers of reducing equivalents, and (2) oxidases. Many of these enzymes are organised in multienzyme systems which function as the terminal respiratory chain. The first process in the terminal respiratory chain consists in the activation of certain specific hydrogen atoms by specific dehydrogenases. The second process involves the transfer of the hydrogen atoms (reducing equivalents) from metabolites to carriers of reducing equivalents. The final stage in terminal oxidation consists in the combination of the reducing equivalents from the carrier with oxygen.