Jinsh

The three primary foodstuffs, carbohydrate, fat and protein, in addition to providing energy for the conduct of vital activities, supply the major proportion of the structural materials of the body and the machinery by which the energy derived from their combustion is converted to useful activities. It has been proposed that the metabolic processes be considered less than two headings, energy metabolism and operative metabolism. The over – all results of the former have been described in the preceding chapter. This and the two following chapters will be devoted to the discussion of the nature of the processes by which the three foodstuffs are oxidized, their intermediary metabolism, and their operative functions. All three foodstuffs are, within limits, interchangeable for purpose of energy production; but each one of the three is indispensable because it has individually specialized operative functions. These are so interlocked that it is actually impossible to treat the three foodstuffs separately in a comprehensive discussion of metabolism. It is, however, convenient to treat them individually so far as intermediary reactions are concerned, beginning with carbohydrates, about which, because of their relative chemical simplicity, the greatest information is available.