Overview

Metabolism focuses on the sum total of all physical and chemical changes that take place within an organism. Derived from the Greek word metabole, meaning "change," it includes all energy and material transformations that occur within a living cell.

Energy is a fundamental feature of life. Processes at the cellular level are the same whether they are in animals, plants, fungi, or bacteria. Living matter is made up of large molecules called proteins, which are assembled from some 20 amino acids.

At the beginning of the nineteenth century, however, people held to traditional beliefs that special biological laws or forces controlled life. This belief, called vitalism, was well entrenched in the romantic thinking prevalent in that period. It is understandable that people who had no knowledge of atoms and molecules would explain life by adopting such ideas to...