1. Electron Transport Chain and ATP Production:
* The electron transport chain (ETC) is a series of protein complexes embedded in the inner mitochondrial membrane.
* Electrons from NADH and FADH₂ are passed along these complexes, releasing energy that pumps protons across the membrane, creating a proton gradient.
* This gradient drives ATP synthesis by ATP synthase.
2. Entry Points of NADH and FADH₂:
* NADH: Enters the ETC at complex I, which has a higher energy level than complex II.
* FADH₂: Enters the ETC at complex II, a lower energy level than complex I.
3. Energy Difference and ATP Yield:
* The difference in energy levels between the entry points of NADH and FADH₂ means that FADH₂ releases less energy as its electrons are passed along the ETC.
* This results in fewer protons being pumped across the membrane, ultimately producing fewer ATP molecules.
4. Theoretical Yield:
* It is generally accepted that NADH produces about 2.5 ATP molecules per molecule, while FADH₂ produces approximately 1.5 ATP molecules per molecule.
In summary:
FADH₂ produces fewer ATP molecules than NADH because it enters the electron transport chain at a lower energy level, resulting in less energy being released and fewer protons being pumped across the mitochondrial membrane.
