Here's how it works:
1. Proton Pumping: Electrons flowing through the electron transport chain (ETC) in the inner mitochondrial membrane pump protons (H+) from the mitochondrial matrix to the intermembrane space. This creates a concentration gradient, with a higher concentration of protons in the intermembrane space than in the matrix.
2. Potential Energy: This proton gradient represents potential energy, just like a dam storing water behind it.
3. ATP Synthase: ATP synthase, embedded in the inner mitochondrial membrane, acts like a turbine. It has a channel that allows protons to flow back down their concentration gradient from the intermembrane space to the matrix.
4. Rotation and ATP Production: As protons flow through the channel, they cause the rotor portion of ATP synthase to spin. This spinning motion powers the catalytic site of ATP synthase, which combines ADP and inorganic phosphate (Pi) to produce ATP.
In summary, the proton gradient created by the electron transport chain provides the driving force for ATP synthase, enabling it to produce ATP from ADP and Pi.
