Which of the following best describes metabolism?

Metabolism is best described as the sum of all chemical processes that occur in a living organism. This encompasses both anabolic reactions, which build up substances and consume energy, and catabolic reactions, which break down substances and release energy. Together, these processes are crucial for maintaining the organism's life, allowing it to grow, reproduce, repair damage, and respond to environmental changes.

Understanding metabolism is central to biology because it highlights how organisms convert food into energy and the myriad of reactions that underpin life functions. The other choices focus on specific aspects related to biological interactions, physical traits, or energy consumption, but they do not capture the comprehensive scope of metabolic processes that involve all chemical reactions taking place within an organism.