Metabolism is the collection of chemical reactions that define a living organism and allow it to make its components and obtain the energy required for staying alive.
Recognition that the processes occurring in a living organism are fundamentally chemical reactions came progressively with the decline in vitalism in the nineteenth century. The discovery of cell-free fermentation by Eduard Buchner sounded the death knell of vitalism and the beginning of the unraveling of the major metabolic pathways that constitute metabolism. This process began with the understanding of fermentation and glycolysis, and by the end of the 1950s, virtually all the major pathways were known.
Although a living organism is identified and recognized by its physical appearance and hence by its structure, its status as living is defined by its chemistry and thus by its metabolism. This is a network of reactions that is responsible...