Lecture 4 Slides rh

Oxidation and Reduction as it pertains to biochemistry

please read Read The Slow Burn

fig 13-22

fig 13-22

reduction potential can be measured ref. cell test cell fig 13-23

Fe3+ + Cu+ Fe2+ + Cu2+ Cu2+ + e- Cu+ Fe3+ + e- Fe2+ Redox reactions as pairs of half-reactions Fe3+ + Cu+ Fe2+ + Cu2+ The half-reactions: Cu2+ + e- Cu+ E'o = -.18 Fe3+ + e- Fe2+ E'o = .77 always reductions! rh

Fe3+ + Cu+ Fe2+ + Cu2+ Cu+ Cu2+ + e- Fe3+ + e- Fe2+ Fe3+ + Cu+ Energetics calculated from half-reactions Fe3+ + Cu+ Fe2+ + Cu2+ what is E'o for this reaction ? Cu+ Cu2+ + e- E'o =.18 Fe3+ + e- Fe2+ E'o = .77 Fe3+ + Cu+ Fe2++ Cu2+ E'o = (.18 +.77) rh

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DG'o = -nFE'o relationship between free energy and reduction potential one confusing thing: by the convention, positive E means spontaneous reaction… or negative DG. rh

Fe3+ + Cu+ Fe2+ + Cu2+ Cu+ Cu2+ + e- Fe3+ + e- Fe2+ Fe3+ + Cu+ Energetics calculated from half-reactions Fe3+ + Cu+ Fe2+ + Cu2+ what is E'o for this reaction ? Cu+ Cu2+ + e- E'o = .18 Fe3+ + e- Fe2+ E'o = .77 Fe3+ + Cu+ Fe2++ Cu2+ E'o = 0.95 rh

DG'o = -nFE'o nFE'o rh

Fe2+ + Cu2+ Fe3+ + Cu+ rh familiar from earlier chemistry classes… BUT WHAT ABOUT SOMETHING LIKE THIS?: glucose rh

Oxidation of a "model" sugar molecule: CH2O glucose general: let's make n=1, to aid understanding rh

Oxidation of a "model" sugar molecule: CH2O 1) removal of electrons from sugar rh

Oxidation of a "model" sugar molecule: CH2O 2) reduction of oxygen rh

Oxidation of a "model" sugar molecule: CH2O 3) production of CO2 rh

Table of Standard Reduction Potentials TOP MIDDLE BOTTOM

NAD+ and NADH fig 13-24

The business end of NAD and NADP this moiety is from the vitamin niacin rh

moi·e·ty (moi-t)n.One of two or more parts into which something may be divided, such as the various parts of a vitamin or molecule. ? this moiety is from the vitamin niacin rh

table 13-8

FAD and FADH2 (and FMN and FMNH2) fig 13-27

isoalloxazine ring The business end of FAD or FMN rh this moiety is from the vitamin riboflavin rh

fig 13-9