What does 'metabolism' describe in living organisms?

Metabolism refers to the set of life-sustaining chemical transformations that occur within the cells of living organisms. These processes enable organisms to grow, reproduce, maintain their structures, and respond to environmental changes. Metabolism encompasses both anabolism, which is the building up of components such as proteins and nucleic acids, and catabolism, which involves breaking down molecules to produce energy. This biochemical activity is essential for all forms of life, as it provides the necessary energy and materials for cells to function properly.

In the context of the other choices, while social interactions and communication between species are important aspects of ecology and behavior in organisms, they do not relate to the biochemical processes that sustain life. Similarly, the process of respiration in plants is a specific metabolic function, but metabolism as a concept is much broader, encompassing all chemical reactions within a cell, including respiration, digestion, and energy transfer.