Electron Transport Chain General Information


          Takes place in inner mitochondrial membrane


          Follows Krebs Cycle in aerobic metabolism


          Energy released to make ATP


          Requires series of oxidation-reduction reactions


          Requires four membrane-bound complexes


          3 ATP produced per NADH


          2 ATP produced per FADH2


          ATP production:


               NADH per glucose: 2 from glycolysis + 8 from Krebs

                cycle = 30 ATP


               FADH2 per glucose: 2 from Krebs cycle = 4 ATP


              2 ATP per glucose from glycolysis + 2 GTP from

              Krebs cycle = 4 ATP


            Total ATP per glucose (under aerobic conditions) = 38    



             Uses oxygen as final electron acceptor


             Completes process by which glucose is converted to

             CO2 and H2O



Complex I: NADH-CoQ reductase


          1.Entry site for NADH + H+


              7 Fe-S cluster (non-heme protein)

              flavin mononucleotide phosphate (FMN)

              Coenzyme Q (free in membrane)

         3.Net reaction: NADH + H+ + CoQ ---> NAD+ + CoQH2

         4.ATP produced










Complex II: Succinate-CoQ oxidoreductase


          1.Entry site for FADH2


             2 Fe-S cluster (non-heme protein)

             Coenzyme Q (free in membrane)

        3.Net reaction: Succinate + CoQ ---> Fumarate + CoQH2

        4.No ATP 


     Complex III: CoQH2-cytochrome c oxidoreductase



             cyctochrome c (free in membrane)

             2 cyctochrome b

             cytochrome c1

             Several Fe-S cluster (non-heme protein)

      2.Net reaction: CoQH2 + 2 cyt c [Fe (III)] ---> CoQ + 2 cyt 

         c [Fe (II)] + 2 H+

      3. ATP produced


     Complex IV: Cytochrome oxidase



             cyctochrome a

             cyctochrome a3

             2 Cu2+

         2.Net reaction: 2 cyt c [Fe (II)] + 1/2 O2 + 2 H+ ---> 2 cyt

            c [Fe (III)] + H2O

         3. ATP produced 








   Pumping of protons creates higher [H+] on cytosolic side of



   Proton motive force drives synthesis of ATP by ATP  



   ATP synthase is composed of two subunits. 


        Fo proton conducting unit 

        F1 catalytic unit: five polypeptide chains. 


       F1 has 3 a and 3 b subunits as well as one g