Explain ETS.

Electron Transport System (ETS) is the series of protein complexes and mobile carriers located in the inner mitochondrial membrane that transfer electrons from NADH and FADH₂ to oxygen, releasing energy coupled to ATP synthesis

• Complex I NADH dehydrogenase oxidises NADH to NAD⁺, transfers electrons to ubiquinone and pumps protons into the intermembrane space

• Complex II succinate dehydrogenase oxidises FADH₂ to FAD and transfers electrons to ubiquinone without pumping protons

• Ubiquinol transfers electrons to Complex III cytochrome bc₁ which pumps protons and passes electrons to cytochrome c

• Cytochrome c shuttles electrons to Complex IV cytochrome c oxidase where protons are pumped and oxygen is reduced to water

Electron transfer through the complexes drives proton pumping across the inner membrane forming an electrochemical proton gradient known as the proton motive force

ATP synthase (Complex V) consists of an F₀ proton channel and an F₁ catalytic head that allows the flow of protons back into the mitochondrial matrix to drive ATP production from ADP and inorganic phosphate

Oxidation of one molecule of NADH yields three ATP and oxidation of one molecule of FADH₂ yields two ATP under theoretical conditions, though actual yields in cells may differ

The coupling of electron transport and ATP synthesis in the presence of oxygen is termed oxidative phosphorylation and relies on oxygen as the final electron acceptor