A nutrient or nutrient is a chemical from outside the cell and it needs to perform its vital functions. It is taken by the cell and transformed into a cellular constituent through a metabolic process of biosynthesis called anabolism, or it is degraded to obtain other molecules and energy and nutrients. Nutrients are any chemical element or compound necessary for the metabolism of a being. alive. That is, nutrients are some of the substances contained in food that actively participate in metabolic reactions to maintain all the functions of the body.