Important for metabolic pathways both in plants and animals is an enzyme called ATP Synthase. This enzyme sits on the high-end side of the proton gradient generated on the membrane either in the mitochondria or the chloroplast. As large amount of protons are pushed upwards the enzyme acts like a pump and generates ATP. It is belived that this enzyme has a rotary like motion.
Hongyun Wang's research in biophysics and molecular modeling is to investigate the mechanism by which chemical energy is converted into mechanical work in biological systems.
The above are cartoon animations of F1 motor and Fo motor of the ATP synthase.
In mitochondria, bacteria, and chloroplasts the free energy stored in transmembrane electrochemical gradients is used to synthesize ATP from ADP and phosphate via the membrane-bound enzyme ATP synthase. ATP synthase can also reverse itself and hydrolyze ATP to pump ions against an electrochemical gradient.