STPM Biology - chapter 5 (old syllabus) chapter 5 (new syllabus): Revision essay question 6

6. Explain how electrons from NADH and FADH₂ flow through  the electron transport chain with the production of ATP.

Answer

-         Electron within NADH and FADH₂ from the Krebs cycle enter the electron transport system which consist of a series of molecules embedded in the inner membrane of mitochondria.

-         Each molecule is an electron carrier.Electron are passed from one carrier to another at progressively lower energy levels.The carrier molecule that receives an electron is reduced,and the one losing the electron is oxidized.

-         Asmall amount of ener_{gy is released during each transfer.}

-         _Electrons from NADH enter the electron transport chain at flavin mononucleotide whereas electrons from FADH₂ enter at lower energy level,that is at ubiquinone molecules.

-         The cytochrome are then oxidized and reduced.

-         The final carrier in the chain,cytochrome aa₃transfer the electrons to oxygen to form water.

-         The energy released by the electron transport chain is used to pump hydrogen ion from the matrix into the intermembrane space.

-         This builds up a transmembrane electrochemical proton gradient.

-         When protondiffuse out from the intermembrane space through the ATP synthetase protein channel into the mitochondrial matrix,ATP is synthesized from ADP and Pi

-         Each NADH generates 3 ATP AND 1 FADH₂ generates 2 ATP.