Sunday, January 4, 2009

Energy generation in the mitochondrion, part 3

This is a continuation of yesterday’s post. We are now in the final phase of energy generation, the oxidative phosphorylation. This process takes place along the cristae of the mitochondrion. This is the reason why I mentioned in one of the previous posts that the more folds or cristae there are, the larger the area for energy generation.

Oxidative phosphorylation is the only phase wherein oxygen is used. However, as mentioned before, preparation for this final phase actually starts during the formation of AcetylCoA from pyruvic acid.

The hydrogen ions and electrons that are generated during the Krebs’ cycle are transferred by the hydrogen acceptors to the different enzymes along the cristae of the mitochondrion. Here the electrons are transferred from one electron acceptor to another along the cristae while the ions are pumped across the cristae to the intermembrane space (see post on the structure of the mitochondrion). The ions thus create a proton gradient across the cristae. This gradient drives the ions to move back to the matrix and as the ions pass through special channels that are associated with ATP synthase, ADP is phosphorylated to ATP.

Oxygen acts as the final hydrogen acceptor as the electrons and ions rejoin each other and form water in the process.

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