Answer
Hydrogen ion movement form ATP in ATP synthase .
Explanation:
ATP synthase is present in mitochondrial membrane when pass hydrogen ion in to lumen of mitochondria and due to proton gradient generate ATP molecule with pass of hydrogen ion into lumen ATP is formed from ADP and inorganic phosphorous molecule . Passing of three hydrogen io generate one ATP molecule .So movement of hydrogen ion is directly related to ATP synthases.
I believe the correct answer is homeostasis.
