Metabolism

In all living organisms chemical reactions take place that are essential to
nutrition, growth and repair of cells, and conversion of energy into usable
forms. The sum of all the chemical activities of the organism is called metabolism. Metabolic reactions occur continuously in every living organism
(Figure 1-3); when they cease, the organism dies.
Each individual cell of an organism constantly takes in new substances,
alters them chemically in a variety of ways, and builds new cellular