The term for a complex organic substance comprised of a chain of amino acids is protein. Proteins play a crucial role in biological processes and contribute to cellular structure, function, and regulation. They are involved in various functions, including enzymatic activity, transport, and signaling within and between cells. The specific sequence of amino acids in a protein determines its three-dimensional structure, influencing its function. Proteins are vital for sustaining life and serve as the backbone of diverse metabolic pathways, making them essential biomolecules in all living organisms.