Cytochrome c oxidase - mechanism of O2 reduction to H2O 1. Two molecules of cyto

Question

Cytochrome c oxidase - mechanism of O2 reduction to H2O 1. Two molecules of cytochrome c sequentially transfer electrons to reduce Cug and hemea 2.Reduced Cu, and Fe in heme a, bind O, c You should know the steps in Complex IV forms a peroxide bridge. | 1The first two electron transfers from Cyt c reduce Cyt a3 and CuB 2. Then those capture an oxygen molecule to form a peroxide bridge, as in Fig #2 3·Two more electrons are channeled down where they add to the O2 and extract 2 “Chemical protons" from the matrix forming two hydroxyls 4. Two more protons are extracted with release of water Plus there is direct pumping of protons by Complex IV proteins... 2H,O 4. The addition of two more 3. The addition of two more protons leads to the release of water. electrons and two more protons cleaves the peroxide bridge. This is the peroxide bridge, I will not ask you to draw this in detail but you should be able to sketch CuB-O2-heme a3 l6

Explanation / Answer

No need to re-sketch the whole molecule. The mistake lies in the Heme moiety.

In the porphyrin part of the heme, four N of the porphyrin ring binds to the metal center Fe. Where as, in the image you have sketched, Fe is bound to 3 N and 1 C atom (the one behind the peroxide bond in the sketch). Just fix that.

Rest are absolutely fine.

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