IUPAC definition : The entire physical and chemical processes involved in the maintenance and reproduction
of life in which nutrients are broken down to generate energy and to give simpler
molecules (catabolism) which by themselves may be used to form more complex molecules
(anabolism). In case of heterotrophic organisms, the energy evolving from catabolic
processes is made available for use by the organism.;
The entire physical and chemical processes involved in the maintenance and reproduction
of life in which nutrients are broken down to generate energy and to give simpler
molecules (catabolism) which by themselves may be used to form more complex molecules
(anabolism). In case of heterotrophic organisms, the energy evolving from catabolic
processes is made available for use by the organism.