ABSTRACT
Metabolism, the sum of all chemical transformations taking place in a cell, is a highly coordinated network of activities in which many multi-enzyme systems and pathways are involved. The purposes of this network can be summarized as follows:
(i) to obtain chemical energy by capturing solar energy or degrading energy-rich nutrients from the environment;
(ii) to convert nutrient precursor molecules into the characteristic macromolecules of the cell;
(iii) to polymerize monomers into macromolecules (proteins, nucleic acids, and polysaccharides);
(iv) to synthesize and degrade biomolecules required for specialized cellular functions, such as membrane lipids, intracellular messengers, and pigments.
