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?

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

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

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

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

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

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

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)

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+)?

Why the correct oxidation state matters

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

The baby died because this reaction didn’t happen: SO H 2 O ---> SO H + + 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.

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

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

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

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

A catalytic cycle for how Mo oxidizes SO 3 2-

The Great Cycle of Energy Derived like this:

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

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

5 Large Protein Complexes in Respiration

Detailed View of One Complex

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