Electron Transport Chain
Electrons from NADH and FADH2 are passed through a series of electron acceptors present in the inner membrane of mitochondria.
- 2 NADH produced during glycolysis,
- 2 NADH, produced during pyruvic acid oxidation, &
- 6 NADH AND 2 FADH2, produced during Kreb cycle.
Four enzyme complexes of ETC
- Complex I – NADH dehydrogenase complex.
- Complex II – Succinate-UQ reductase complex.
- Complex III – UQH2-cytochrome c reductase complex.
- Complex IV – Cytochrome c oxidase complex.
- When NADH is passed through ETC, complex I, III and IV are involved & 6 pairs of H+ are pushed into the intermembrane space.
- When FADH2 is passed through ETC, complex II, III and IV are involved & 2 pairs of H+ are pushed into the intermembrane space.
F0– F1 particles/ ATPase complex (Chemiosmotic Hypothesis)
- The inner membrane is impermeable to H+ .
- So, they return back with the help of F0– F1 particles/ ATPase complex present in the inner membrane.
- 1 ATP is synthesized by the ATPase complex for every 2 H+ passing through the proton tunnel.
- As oxidation of NADH/ FADH is responsible for the formation of ATP it is also referred as oxidative phosphorylation.