Oxidative Phosphorylation

Oxidative Phosphorylation

1. complex 1

   • largest
   • NADH --> NAD+H+2e-
   • 2e- + 2H+ + ubiquinon (Q) --> ubiquinol (QH2)
     • hydrophobic molecule - not a protein
   • electrons pass through iron-sulpher proteins
     • allows H+ to be pumped across

2. complex 2

   • succinate + Q --> fumerate + QH2

3. complex 3

   • step 1
     • QH2 oxidised release 2e-
       • cytochrome accept 1 e-
         • 2H+ pumped across
           • remaining e- rebinds to Q forming Q-
   • step 2
     • Second QH2
       • extra e- binds to Q- with 2H+
         • reforming QH2
           • shuttling

4. complex 4

   • cytochrome C loses 4e-
     • pump 4H+
     • reduce O2 to H2O

5. ATP synthase

   • H+ ions move down electrochemical gradient through complex
     • Y unit (central axis)
       • rotates
         • B subunit cycles between states
           • open/empty - ADP and Pi bind- lose
           • tight - bind to produce ATP
             • cycles back to release 34 ATP

6. end products ATP

   • inhibit
     • at rest
       • increase proton motive force and low flow of protons/e- transfer

7. start products ADP

   • activate
     • during exercise
       • increase proton movement, decrease in proton motive force

8. inhibition

   • inhibit electron chain in complex 4
     • bind to O2
       • carbon monoxide, cyanide
   • inhibit ATP synthase
     • block h+ flow
     • uncoupling agents
       • prevent proton gradient
       • generate heat
         • protons flow but don't produce ATP