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The transfer of energy of a given form among different scales of motion. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed). In biochemistry, this concept generally refers to the transfer of groups from compounds that contain energy-rich bonding arrangements to compounds that have relatively energy-poor bonding characteristics via thermodynamically permissible enzymatic reactions. This principle is a major premise of the interaction between energy-producing and energy-utilizing metabolic pathways in living cells. (From Devlin, Textbook of biochemistry with clinical correlations, 3d ed, p246)