Which best defines metabolism?

Metabolism refers to the totality of an organism's chemical reactions, encompassing a broad array of processes that involve the conversion of food into energy and the building and breaking down of molecules within cells. This definition captures the essence of metabolism, which includes both catabolic reactions (breaking down molecules to release energy) and anabolic reactions (using energy to construct components of cells such as proteins and nucleic acids).

In a broader context, metabolism maintains homeostasis, supporting vital functions in the body and allowing for the growth and repair of tissues. Thus, understanding metabolism is crucial in fields like nutrition, fitness, and health, where the energy balance and metabolic pathways play a significant role in overall well-being and physical performance.