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2010-03-02 19:41:01
Oxidative Phosphorylation

Oxidative Phosphorylation
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  1. What is the role of Complex 1 (NADH-Q oxidoreductase)
    Complex one serves as a proton pump, transporting protons from the mitochondrial matrix to the intermembrane space. NADH donates a e- to the electron carrier flavin. Flaven then transfers the e- to coenzyme Q, which reduces coQ yeilding QH2. As this occurs 4H+ are pumped across the mitochondria membrane.
  2. Explane the role of complex 2.
    Complex 2 (succinate-Q reductase, succinate dehydrogenase) uses FAD+/FADH as an e- source, which it transfers to coQ.
  3. Describe the role of complex 3 (Q-cytochrome c oxidoreductase).
    • There at 2 parts of the complex 3 rxn.
    • The first half uses a QH2 from the Q pool and a oxidized Q. Both of the e- held by QH2 will be dropped, one will got to the oxidized Q, yeilding Q- and the other will go to Cyt C. The oxidized QH2 now Q will leave the complex and return to the Q pool to be reduced again and the 2 H+ will be pumped out.
    • The second half of the rxn uses a new QH2 from the Q pool and the Q- from the first half of the rxn. Again, the QH2 drops both e-. One goes to Cyt C and the other goes to Q-. The oxidized QH2 now Q will return to the Q pool and the H+ will be pumped out. The newly reduced QH2 will return to the Q pool to be used again.
    • This process yeilds 2 Cyt C holding 1 e- each, 4 H+. It will use 2 QH2 and 1 Q which will leave as 2Q and 1 QH2.
  4. Explain the role of Complex 4 (cytochrom c oxidase).
    • There are 4 steps in complex 4.
    • 1) 2 cyt C molecules transfer e- to reduce CuB and Fea.
    • 2) The reduced CuB and Fea are bound by 2O forming a peroxide bridge.
    • 3) 2 more cyt C molecules deposit 2 more e- and 2 H+ are added cleaving the peroxide bridge
    • 4) 2 more H+ are added releasing H20 and pump 2 H+ out of the matrix.

    Therefore, 4 cyt C are needed to proved 4 e- to yeild H2O and pump out 2H+
  5. What is the role of ubiquinone, coenzyme Q, Q?
    Coenzyme Q serves as an electron carrier, coming in contact with complex's 1,2,3. At complex's 1 and 2 Q will gain 1 e- at each step creating a QH2 molecule after complex 2. The QH2 will then drop both of its e- in complex 3 to produce, reduced Cyt C.
  6. Explain the role of Cytochrome C.
    Cyt C is an e- carrier, that is recduce in both parts of the rxn that occurs at complex 3. Cyt C is then used at complex 4 for reduce CuB and FEa, which are then oxidized to yeild H2O and pump 2 H+.
  7. At what site to the e- from NADH enter the ETC?
    NADH transfers its e- to the ETC at complex 1.
  8. At what site does FADH2 transfer its e- to the ETC?
    FADH2 transfers its e- to the ETC at complex 2.
  9. Identify the which complex the following are from; flavin mononucleotide, iron/sulfer cluster, cyt BL, cyt BH, cyt C1, CuA, heme a, Heme a3 and CuB
    • Complex 1 : flavin mononucleotide,
    • Complex 2 : Fe/S clusters
    • Complex 3 : Cyt C1, Cyt C
    • Complex 4 : CuA, CuB,
  10. Which complexes act as proton pumps in ETC?
    Complexes 1, 3 and 4. Complex 1 and 3 transport 2 H+ each and complex 4 transports 2 H+.
  11. What is the role of complex 5 (ATP synthase)
    complex 5 pumps in 10 H+ from the cytoplasm into the mitochondrial matrix to make 3 ATP.
  12. How does the ATP synthase use the proton gradient generated by the ETC to make ATP?
  13. What factors influence the rate of e- movement through the ETC?

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