The chemiosmotic hypothesis put forth by Sir Peter Mitchell suggests that the proton gradient created across the inner membrane of mitochondria is responsible for the pumping of H+ ions into the mitochondrial matrix. This energy produced by the proton pump is harnessed by the catalytic subunit of ATPase enzyme complex to produce ATP. A similar mechanism is seen in the thylakoid membrane of chloroplast during energy production in the light reaction of photosynthesis.