Explain ETS.

The electron transport system (ETS) is also called Oxidative Phosphorylation. It is present in the inner mitochondrial membrane. It's a metabolic pathway that allows electrons to go from one carrier to the next. The passes of electrons from NADH and 2 FADH to oxygen (O₂) is facilitated by five multiprotein complexes in the ETS. The complexes are: 

Complex I (NADH dehydrogenase), Complex II (Succinate dehydrogenase),
Complex III ( 1 Cytochrome bc Complex ), Complex IV (Cytochrome c oxidase) and
Cytochrome V (ATP Synthase). The steps involved in ETS are as follows:

1. Electrons from NADH produced in the inner mitochondrial matrix during the citric acid cycle are oxidized by NADH dehydrogenase (Complex I).

2. Post this, electrons are transferred to Ubiquinone which receives reducing equivalents via FADH₂ (Complex II).

3. Ubiquinol (reduced ubiquinone) is then oxidized with the transfer of electrons to Cytochrome c via Cytochrome bc₁ Complex (Complex III).

4. Cytochrome c oxidase Complex (Complex IV) contains cytochromes a,a₃ and two Cu centres.

5. When electrons travel from one carrier to another in the electron transport chain via complex I to IV, they are connected to ATP Synthase (complex V).

6. Complex V consists of components like F₁ (peripheral membrane protein complex) and F₀ (integral membrane protein complex). At F₁ATP is synthesized from ADP and Pi. Protons passing through channels formed by F₀ are coupled to the catalytic site of F₁ .

7. One molecule of NADH (oxidized) provides 3 molecules of ATP. One molecule of FADH₂ produces 2 molecules of ATP.