What is the sum of all chemical reactions that occur within an organism called?

The sum of all chemical reactions that occur within an organism is called metabolism. Metabolism encompasses a variety of biochemical processes that convert food into energy, build cellular structures, and manage waste products. It is a comprehensive term that includes both catabolic pathways, which break down molecules to generate energy, and anabolic pathways, which use energy to construct components of cells such as proteins and nucleic acids.

Understanding metabolism is crucial because it represents the entire network of chemical reactions that sustain life, from nutrient breakdown to energy production and growth. In contrast, the other terms, while related to aspects of metabolism, refer to more specific processes: respiration focuses on how organisms produce energy through the intake and conversion of oxygen and glucose, synthesis refers to the creation of molecules from simpler units, and anabolism is specifically the constructive aspect of metabolism where small molecules are built into larger, more complex ones.