Question

In the electron transfer system, it has been mentioned in prior questions that complexes I, III, and IV are proton pumps and that these pumps pump protons from the matrix into the intermembrane space. Does the formation of water inside the mitochondrial matrix help contribute to the proton gradient during the electron transport chain?Electron Transport Chain Proton Pumping into the Intermembrane SpaceHow many protons are pumped out per pair of electrons from NADH in oxidative phosphorylation? My question.However, where are the protons in the matrix supplied from?In other words, where does the OH- generated when the protons are generated in the matrix disappear?Why is it not biased to the alkaline side to the extreme even though the number of proton is decreasing rapidly due to being pumped out or used to dispose of surplus electrons? In particular, it seems that theProtonsin the matrix are used to dispose of surplus electrons in the electron transfer system by combining with externally introduced O2 to produce H2O, but this seems to result in too much OH-. I would like to know the fate of the excess alkali.

Answer 1

The formation of water does not contribute to the proton gradient in the electron transport chain. Protons in the matrix are supplied from NADH and FADH2, and the OH- ions generated are neutralized by the ATP synthase. This helps maintain the pH balance in the matrix.

Step-by-step explanation:

In the electron transport chain, the formation of water inside the mitochondrial matrix does not directly contribute to the proton gradient. The main role of water is to accept the electrons and protons at the end of the electron transport chain, combining with oxygen to form water. This helps ensure the continuation of the electron transport chain and the production of ATP.

The protons in the matrix are supplied from two sources: the transfer of protons from NADH in complex I and the transfer of protons from FADH2 in complex II. These protons are then pumped across the inner membrane into the intermembrane space by complexes I, III, and IV, creating the proton gradient.

The OH- ions generated when protons are pumped out of the matrix combine with H+ ions to form water molecules. The presence of OH- ions does not lead to extreme alkalinity in the matrix because the mitochondrial inner membrane is impermeable to OH- ions. The overall pH balance is maintained by the action of a specific protein, called the ATP synthase, which allows the influx of protons back into the matrix, helping neutralize the OH- ions.