[xxabcxx]

hello everyone--
i got a question about the proton movement/ electron movement during the reduction or oxygen in complex IV.

So then, 4 electrons bring 4 protons to form 2 H2O.  Since those 4 H+ are used to form H2O.  How can there are 4 more protons pumped out to the outside?  Unless 1 electron can carry 2 H+ but doesnt make any sense to me.  Thanks!
 

[Yggdrasil]

Complex IV uses the energy gained from the transfer of electrons to H⁺ and O₂ to pump four additional protons across the mitochondrial inner membrane.  Therefore, complex IV contributes to the proton gradient in two ways: 1) by using up four protons in a chemical reaction (to form water) and 2) by transporting four more protons across the membrane.