Final answer:
ATP synthase works as a molecular motor, using the electrochemical gradient of protons to generate mechanical energy that drives the synthesis of ATP from ADP and Pi.
Step-by-step explanation:
When ATP synthase pumps H+ across a membrane against the electrochemical proton gradient, ATP synthase catalyzes the formation of ATP from ADP and Pi. This process is referred to as chemiosmosis, and it is part of the cellular respiration cycle known as oxidative phosphorylation, where the energy from the electrochemical gradient is harnessed to form ATP.
ATP synthase operates like a tiny generator, using the flow of protons (H+) down their electrochemical gradient through the enzyme to produce mechanical energy that drives the formation of ATP. The process of ATP synthesis from ADP and inorganic phosphate (Pi) involves the rotational parts of ATP synthase, which essentially work as a molecular motor, turning due to the force of H+ ions diffusing through it, thereby generating ATP.
The electrochemical proton gradient formed by ATP synthase causes hydrogen ions (H+) to flow back across the membrane into the matrix, where their concentration is lower. This flow of hydrogen ions occurs through the ATP synthase complex, which acts as a channel protein. Additionally, ATP synthase functions as an enzyme, catalyzing the formation of ATP from ADP and Pi. The energy from the flow of hydrogen ions through ATP synthase is used to drive the synthesis of ATP.