1. NADH₂ and FADH₂ produced during glycolysis, connecting link reaction and Krebs cycle are oxidized with the help of various electron carriers and enzymes. 

2. These carriers and enzymes are arranged on inner mitochondrial membrane in the form of various complexes as complex I, II, III, VI and V. 

3. NADH+H⁺ is oxidised by NADH dehydrogenase (complex I) and it’s electrons are transferred to ubiquinone (coenzyme Q-CoQ) present on inner membrane of mitochondria. Reduced ubiquinone is called as ubiqunol. 

4. FADH₂ is oxidised by complex II (Succinate dehydrogenase) and these electrons are also transferred to CoQ.

5. During oxidation of NADH+H⁺ and FADH₂ , electrons and protons are released but only electrons are canned forward whereas protons are released into outer chamber of mitochondria (intermembrane space). 

6. Ubiquinol is oxidised by complex-III (Cytochrome bcl complex) and it’s electrons are transferred to cytochrome C. Cytochrome C is a small, ironcontaining protein, loosely associated with inner membrane. It acts as a mobile electron carrier, transferring the electrons between complex III and IV. 

7. Cytochrome C is oxidised by complex IV or cytochrome C oxidase consisting of cytochrome a and a₃ . Electrons are transferred by this complex to the molecular oxygen. This is terminal oxidation. 

8. Reduced molecular oxygen reacts with protons to form water molecule called as metabolic water.

9. Protons necessary for this are channelled from outer chamber of mitochondria into inner chamber by F₀ part of oxysome (complex V) present in inner mitochondrial membrane. 

10. This proton channelling by F₀ is coupled to catalytic site of F₁ which catalyses the synthesis of ATP from ADP and inorganic phosphate. This is oxidative phosphorylation. 

11. As transfer of protons is accompanied with synthesis of ATP, this process is named as ‘Chemiosmosis’ by Peter Mitchell.