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Biology - oxidative phosphorylation

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Some things I don't understand:

If oxygen accepts electrons from the electron transport chain, how does it become a molecule of water? ie where does the hydrogen come from?

In chemiosmosis, protons are pumped against their concentration gradient across the inner mitochondrial membrane to create a pH gradient which then powers ATP synthesis. But doesn't the initial pumping out of protons use ATP?

  • Biology - oxidative phosphorylation -

    The hydrogen ions are pumped into the intermembrane space from the mitochondrial matrix. Oxygen captures the electrons in the very last step in the electron transport and adding electrons to that oxygen atom and two hydrogen ions form water.

    No. ATP synthase transports hydrogen ions and it's powered by the flow of hydrogen ions back across the membrane. Those backed-up hydrogen ions will give up their energy when they diffuse through a special protein in the membrane (ATP synthase). That pH gradient will power the pumping - not ATP.

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