Chapter 10 Chem 341 Suroviec Fall 2016

I. Introduction Redox reaction that releases electrons into mitochondrial electron transport chain Mitochondrial electron-transport chain Electrons transferred to other substances to participate in additional oxidation rxns Transferred electrons participate in sequential redox reactions of multiple redox centers in 4 enzyme complexes During electron transfer protons are expelled making a proton gradient

A. Mitochondrial Anatomy Contains Pyruvate dehydrogenase CAC enzymes Enzymes and redox proteins for electron transport and oxidative phosphorylation B. Mitochondrial Transport Outer membrane contains proteins allows diffusion of proteins Intermembrane space equivalent to cytosol

1. Cytosolic Reducing Equivalents NADH produced in cytocol must gain access into mitochodrial electron transport chain Inner membrane does not have NADH transport protein Only the electrons from cytosolic NADH are transported

II. Electron Transport In a redox reaction there are electrons transferred Reduction Potentials Indicates a substance’s ability to accept electrons

Example Calculate the reduction potential of substance A when E = 0.5V, [Ared] = 5 x 10-6M, [Aox] = 2 x 10-4M and n = 2

B. Free Energy Change DG can be calculated from Eo’ electrons flow spontaneously from substance with lower Eo’ to higher Eo’ Example In yeast, alcohol dehydrogenase reduces acetaldehyde to ethanol. Find DGo’

B. Sequence of Electron Transport Oxidation of NADH and FADH2 is carried out by electron transport chain Set of protein complexes containing redox centers with progressively greater affinities for electrons

1. Complex I Passes electrons from NADH to CoQ Contain FMN Contain iron – sulfur clusters

2. Complex II Contains succinate dehydrogenase Passes electrons from succinate to CoQ

3. Complex III Passes electrons from reduced CoQ to cytochrome c

Q - Cycle In complex III need to transport 1 electron at a time from CoQ through cytochromes

4. Complex IV Catalyzes one electron oxidation of 4 consecutive reduced cytochrome c molecules Reduces oxygen

Inhibitors of electron transport

III. Oxidative Phosphorylation Chemiosmosis Free energy of electron transport is conserved by pumping H+ from matrix to intermembrane space Gradient makes ATP synthesis possible

Binding change mechanism B. ATP synthase Multisubunit: F1 and F0 Binding change mechanism

IV. Control of Oxidative Phosphorylation Concentrations of intermediates and energy currency turn on/off oxidative phosphorlyation