During oxidative phosphorylation, ATP is generated as a key product. This process occurs in the inner mitochondrial membrane and is the final stage of cellular respiration, following glycolysis and the citric acid cycle.
In oxidative phosphorylation, electrons from NADH and FADH2 are transferred through a series of protein complexes (the electron transport chain) embedded in the membrane. As electrons move through these complexes, they release energy, which is used to pump protons (H+) across the membrane, creating a proton gradient. The flow of protons back across the membrane through ATP synthase drives the conversion of ADP and inorganic phosphate into ATP.
Thus, ATP is synthesized as a direct result of the proton motive force established during this process, making it the correct answer to the question. The other options—glucose, NADH, and oxygen—though important in cellular respiration, are not the direct products of oxidative phosphorylation itself.