Final answer:
The smallest living functional unit in the human body is the cell, where metabolism, including anabolic and catabolic reactions, occurs.
Step-by-step explanation:
The cell is the smallest living functional unit in the human body, where metabolism takes place. A cell is the smallest independently functioning unit of a living organism, including bacteria, which are single-cell organisms. The body's metabolism involves both anabolic and catabolic reactions that deal with how the organism manages material and energy resources; these processes occur within cells.