1. Step 1: NADH2 is oxidized to release high-energy electrons (e-) and energy. The released electron carrier is taken up by NADH-Q reductase. The energy generated here drives the proton (H+) out of the inner membrane. Here an ATP is produced.
2. Step 2: Electrons are then transferred from NADH-Q reductase to the carrier ubiquinone (Co-Q). Next the electron (e-) from ubiquinone reaches the carrier cytochrome-b.
3. Step 3: FADH2 is oxidized to release high energy electrons (e-) and energy. The released electron carrier is taken up by cytochrome-b. The energy generated here drives the proton (H+) into the intermembrane space. Electrons then pass from cytochrome-B to carrier cytochrome-C.
4. Step IV: Electrons (e-) are transferred from cytochrome-C to cytochrome oxidase. Here the existing proton (H+) is sent to the intermembrane space. Finally, electrons are released into the mitochondrial matrix and combine with O2 to form H2O water.
5. Fifth step: Protons from the intermembrane space are re-entered into the matrix by ATP synthase in the process of chemi-osmosis. Here the energy released combines ADP and Pi to form ATP.
6. Sixth step: Electrons (e-) and protons (H+) react with oxygen in the matrix to produce H2O. The process stops when an oxygen vacancy occurs in the matrix.