There are five protein complexes in inner mitochondrial membrane. NADH+H+ and FADH2 gives electrons to these complexes that have electron carriers. As the elctros move from one carrier to another oxidation reduction reaction takes place, and energy release is used to pump H+ fro matrix to intermembrane space of mitochondria, leading to proton gradient.
These protons pass through last complex channel by chemiosmosis to form ATP from the energy released.
