What term best describes the totality of chemical reactions that occur within a living organism?

The term that best describes the totality of chemical reactions that occur within a living organism is metabolism. Metabolism encompasses all the biochemical processes that contribute to the maintenance of life, including the transformation of energy and the synthesis and degradation of molecules necessary for cellular function. It involves two primary categories: catabolism, which breaks down molecules to release energy, and anabolism, which builds complex molecules from simpler ones. Understanding metabolism is crucial for examining how organisms convert food into energy, synthesize necessary compounds, and maintain overall homeostasis. This differentiation is essential for students focusing on the intricate processes supporting biological functions.