What is metabolism?

Metabolism encompasses all biochemical reactions that occur within an organism to maintain life. This includes both the conversion of nutrients into energy and the processes that use that energy to create the building blocks needed for growth, reproduction, and maintenance of cellular functions. Specifically, the process of converting nutrients into energy is a key aspect of metabolism, as it allows cells to perform their necessary functions and sustain life.

While the other choices touch on important biological processes, they do not encompass the full definition of metabolism. For instance, the breakdown of toxins relates more to detoxification processes rather than the broader scope of metabolism itself. Cellular respiration is indeed a component of metabolism but does not fully capture the entirety of metabolic processes, which also includes anabolism (building molecules) and catabolism (breaking them down). Additionally, the storage of unused energy is a part of metabolic regulation but is not representative of the totality of metabolic activities. Overall, the conversion of nutrients into energy is central to understanding metabolism as it highlights how organisms utilize the substances they consume to fuel life processes.