Final answer:
ATP synthase is a large macromolecule, around 550 kDa, comprised of protein subunits that synthesize ATP by using a proton gradient to facilitate the conversion of ADP and inorganic phosphate into ATP.
Step-by-step explanation:
The enzyme ATP synthase is a complex macromolecule that functions as a molecular motor to synthesize ATP. It consists of multiple protein subunits forming two main parts: the Fo portion, embedded in the inner membrane of mitochondria, and the F1 portion, which protrudes into the mitochondrial matrix. The Fo part uses a proton (H+) gradient to rotate and drive the conformational changes in the F1 part, which in turn catalyzes the conversion of ADP and inorganic phosphate (Pi) into ATP. As a biological structure and a key enzyme, ATP synthase has a high molecular mass of approximately 550 kDa and is essential for energy production in cells.