Final answer:
As electrons move through the electron transport chain, they drive the pumping of H+ ions to create a proton gradient across the inner mitochondrial membrane, which is then used to synthesize ATP.
Step-by-step explanation:
As electrons pass through the electron transport chain, they are transferred from carrier to carrier and their energy is harvested to perform work within the cell. This work includes the pumping of hydrogen ions (H+) across the inner mitochondrial membrane to create a proton gradient.
The energy from this gradient is then used to drive the synthesis of ATP, the cell's energy currency, via the enzyme ATP synthase. Furthermore, the final step in this process involves electrons reducing oxygen to form water, completing the transfer of energy from high-energy molecules NADH and FADH2 to ATP synthesis.