E.T.C. -Key Words.
The Electron Transport Chain is a series of membrane proteins located on the inner mitochondrion membrane.It functions in linking two very important processes, electron transport and oxidative phosphorylation. Acording to thermodynamics, an unfeasable reaction can be made to occur by coupling (linking) it to a feasable reaction. The mitochondrion makes use of this concept. The ETC is composed of five membrane transport proteins, Complex 1-4 and ATP Synthase (Complex 5). Complex 1 accepts electrons from NADH+H while complex 2 accepts electrons from FADH2. The electron donors are oxidised while thecomplexes are reduced (a redox reaction). Both complexes then delivers these electrons to the more electropositive complex 3. Complex 3 delivers its electrons to the more electropositive complex 4 which delivers them to oxygen in the formation of water.In this way, electrons move along an electropotential gradient. Complexes 1,3, and 4 also function as proton pumps.The energy gained from moving electrons along their electropotential gradient is used to actively transport protons against their concentration gradient from the mitochondrial matrix to the intermembrane space. ATP synthase functions as a proton channel, allowing protons to diffuse back into the mitochondrial matrix. The energy gained from this processis used to add a phosphate group to ADP to form ATP. Thus electron transport is linked to oxidative phosphorylation by the Electron Transport Chain.
