The right answer is metabolism.
Metabolism defines the set of coupled reactions occurring in the cells of the body. It consists of two opposing mechanisms:
* Catabolism: it allows the extraction of energy from nutrients, by degradation of energy molecules (carbohydrates, lipids ...);
* Anabolism: it allows to synthesize the constituents necessary for the structure and the proper functioning of the cells.
Basal metabolism is also contrasted with metabolism in activity.