Which term describes the total sum of all chemical reactions occurring in an organism?

The term that describes the total sum of all chemical reactions occurring in an organism is metabolism. Metabolism encompasses both the processes that break down substances to produce energy (catabolism) and those that build up molecules needed by the organism (anabolism). Essentially, metabolism includes all biochemical pathways and reactions that enable an organism to maintain life, grow, reproduce, and respond to the environment.

Homeostasis refers to the ability of an organism to maintain a stable internal environment despite external changes, which is a result of metabolic processes but does not encompass all reactions themselves. Catabolism specifically refers to the breakdown of complex molecules into simpler ones to release energy, while anabolism refers to the synthesis of complex molecules from simpler ones, often requiring energy. Metabolism is the overarching term that includes both of these processes and more, accurately reflecting the totality of chemical reactions in an organism.