Which of the following best describes metabolism?

Metabolism encompasses the entirety of biochemical processes that occur within the body, which includes both catabolism (the breakdown of molecules to obtain energy) and anabolism (the synthesis of all compounds needed by the cells). By describing metabolism as "the sum of all chemical reactions in the body," it captures the full scope of how the body transforms food into usable energy while regulating bodily functions, maintaining homeostasis, and facilitating growth and repair.

Other choices, while they touch on aspects of metabolism, do not fully encapsulate its comprehensive definition. The ability to store energy and the breakdown of carbohydrates are components of metabolic processes but do not represent the complete picture that is conveyed in the correct answer. Additionally, focusing solely on the conversion of food into nutrients overlooks the numerous reactions involved in metabolic pathways essential for overall health and energy balance.