Final answer:
ATP synthase is powered by an electrochemical proton gradient established by the Electron Transport Chain. Protons flow through ATP synthase, catalyzing the transformation of ADP into ATP, a process tightly regulated by the ATP/ADP ratio within the mitochondrial matrix.
Step-by-step explanation:
The concentration gradient that powers ATP synthase is generated by the Electron Transport Chain (ETC), which moves electrons through a series of redox reactions, leading to the accumulation of protons (H+) within the mitochondrial matrix. This results in an electrochemical gradient with a higher concentration of protons outside the inner mitochondrial membrane compared to the inside. The proton gradient provides the potential energy necessary for ATP synthase to function.
As protons flow back across the inner mitochondrial membrane through ATP synthase, the enzyme utilizes this energy to add a phosphate to ADP, forming ATP by a process known as oxidative phosphorylation. For every three to four protons that flow through, one molecule of ATP is synthesized. This action resembles how water flowing through a turbine generates electricity.
ATP synthesis can be regulated by the ATP/ADP ratio within the mitochondrial matrix. A high ATP/ADP ratio indicates that additional ATP synthesis is not required, causing the proton gate to remain closed and preserving the proton gradient. Conversely, a low ATP/ADP ratio signals the need for more ATP, allowing the proton gate to open and protons to flow through ATP synthase, turning the molecular machine and enabling the synthesis of ATP.