Complex IV of the mitochondrial electron transport chain contains two separate c

Question

Complex IV of the mitochondrial electron transport chain contains two separate copper containing complexes. Cus contains two Cu ion bridged by S ions and each coordinated to two S atoms from cysteine residues. Cug contains a Cu ion triply coordinated to N atoms from three different histidine residues. The one-electron reduction potential of Cu* in Cus is 0.254 V while in Cug it is 0.340 V. Comment on role of the chemical environment in determining the stability of the redox species. on potential of Cu?* in Cu is 0.254

Explanation / Answer

In IUPAC system, if reduction potential is more positve then reduction is easier. Here, in CuB reduction potential is 0.340V which is more positve than CuA (0.254V). Therefore one electron reduction of Cu2+ in CuB is favourable which indicates that triply coordinated Cu ion's chemical environment is electron deficient and comparatively unstable in oxidized state, on the other hand CuA ions are stable in oxidized state because their chemical environment is electron rich.

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