25 atp from 10 reduced nad? Watch

debbie394
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why does 10 molecules of reduced nad produce 25 molecules of atp
and why do the protons and electrons from two molecules of reduced fad produce the molecules of atp?
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Jpw1097
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(Original post by esmeralda123)
why does 10 molecules of reduced nad produce 25 molecules of atp
and why do the protons and electrons from two molecules of reduced fad produce the molecules of atp?
NADH => NAD+ + 2e- + H+
FADH2 => FAD + 2e-+ 2H+

The electron transport chain is made up of 4 complexes. Complex I pumps 4H+ from the mitochondrial matrix into the intermembranous space, complex III pumps 4H+ also, while complex IV only pumps 2H+ - complex II does not pump any H+ into the intermembrane space. For ATP to be generated, these H+ ions (protons) diffuse down their electrochemical gradient from the intermembrane space into the matrix via ATP synthase, which essentially 'spins' and forms ATP from ADP and an inorganic phosphate - this is known as chemiosmosis. For each molecule of ATP, 4 protons must flow through ATP synthase.
These complexes are powered by high-energy electrons which come from NADH and FADH2. These electrons are then passed from complex I to CoQ, to complex III, to cytochrome C, to complex IV (cytochrome C oxidase) and finally to O2 - the final electron acceptor. O2 picks up these electrons, along with protons (H+ ions) to form water. With each electron transfer, the electrons transfer energy to the proton pumps/complexes, which allows them to pump protons against their electrochemical gradient into the intermembrane space.
The electrons from NADH enter the electron transport chain at complex I - therefore, for each molecule of NADH, 10H+ are formed (via complex I, III and IV). Therefore, for each molecule of NADH, 10H+ are produced and so 2.5 ATP are produced (since 4H+ are needed for 1 ATP). However, electrons from FADH2 bypass complex I and enter the electron transport chain at complex II. Therefore one molecule of FADH2 only produces 6H+ (4H+ from complex III and 2H+ from complex IV), which produces 1.5ATP.
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