1. Previously in Chem104: Redox reactions are donor-acceptor chemistry like acid/base reactions Important Equations: E rxn = E red + E ox  G = -n F E rxn (Faraday Law) Today in Chem104: Standard Reduction Table (trends) Balancing Redox Equations (#1-easy) (#2-harder) Why the Correct Oxidation State Matters The Great Cycle of Energy Not at Standard?

2. First, a recap of terms! Redox Terminology 1.Electron Donation: Done by the Reductant = Reducing Agent Causes the reductant to become oxidized Occurs in the Oxidation Half Reaction 2.Electron Acceptance: Done by the Oxidant = Oxidizing Agent Causes the oxidant to become reduced Occurs in the Reduction Half Reaction 3.The Processes Oxidation = Loss of Electrons Reduction = Gain of Electrons

3. a question from Monday remains to be answered: Where is the additional oxygen atom in the oxidized glucose from? - 2 e- C 6 H 12 O 6 C 6 H 12 O 7

4. But first, let’s practice. Exercise 1. (easy) Write spontaneous redox equations Example: Pick any two redox couples.

5. How Do I Choose E red + E ox ? You need to know the TRENDS Let’s get a closer look….

6. TABLE OF STANDARD REDUCTION POTENTIALS E o (V) Cu 2+ + 2e-  Cu+0.34 I2I2 + 2e-  2 I-+0.53 Zn 2+ + 2e-  Zn-0.76 stronger reducing ability Ag + + e-  Ag+0.80 Fe 3+ + e-  Fe+0.77 2+ Pb 2+ + 2e-  Pb-0.13 Fe 2+ + 2e-  Fe-0.44 Al 3+ + 3e-  Al-1.66Na + + e-  Na+2.71 K + + e-  K+2.93 2 H + + 2e-  H 2 0.00 stronger oxidizing ability

7. But first, let’s practice. Exercise 1. (easy) Write spontaneous redox equations Example: Pick any two redox couples.

8. Back to this question: Where is the additional oxygen atom in the oxidized glucose from? - 2 e- C 6 H 12 O 6 C 6 H 12 O 7 + H 2 O - 2 H+ - 2 e- Water often is needed to balance redox equations when there is a difference of O atoms on each side (this is the harder type of redox balancing problem)

9. Next, more practice! Exercise 2. (harder) Write spontaneous redox equations An Example to get going: What is the spontaneous redox rxn Between nitrate and Fe(2+)?

10. Why the correct oxidation state matters

11. MRI of brain of deceased baby with Sulfite Oxidase Deficiency MRI of a healthy infant brain

12. The baby died because this reaction didn’t happen: SO 3 2- + H 2 O ---> SO 4 2- + 2H + + 2e- Sulfite Sulfate S 4+ S 6+ The baby has a genetic defect in the enzyme that catalyzes this reaction. Babies with this genetic disease die within hours. The enzyme is Sulfite Oxidase. You have it in your liver.

13. Oxidation SO 3 2- + H 2 O ---> SO 4 2- + 2H + + 2e- half reaction S 4+ in Sulfite S 6+ in Sulfate Reduction Mo 6+ + 2e- ---> Mo 4+ half reaction Net redox reaction SO 3 2- + H 2 O + Mo 6+ ---> SO 4 2- + 2H + + Mo 4+ Review the terms: Is this reaction spontaneous?

15. If you look deeper into the protein…. You find this: The Molybdenum Cofactor

16. + Mo defective molybdoenzymes Can Human Molybdoenzyme Deficiencies Be Cured with more Mo? Not repaired by adding Mo alone Non-functional enzyme

17. SO 4 2- Mo S S S Big Ligand on Mo Cysteine, Amino acid Ligand on Mo O O

18. A catalytic cycle for how Mo oxidizes SO 3 2-

19. The Great Cycle of Energy Derived like this:

20. The Great Cycle of Energy GG EK eq  G = -RTlnK  G = -n F E rxn lnK = (nF/RT)E rxn

21. Electron Transfer Reactions: NOT just for Metals! NOT just about batteries! It’s EVERYWHERE in biology!!

22. 5 Large Protein Complexes in Respiration

23. Detailed View of One Complex

24. oxy peroxy Ferryl The Mechanism of O 2 Reduction to Water - H 2 O