BIOL0280 Lecture 10 - Oxidative Phosphorylation Notes PDF

Preview

Summary

Lecture 10 Review Notes
Professor Lapierre and Professor Salomon...

Description

BIOL0280 – Lecture 10 – Oxidative Phosphorylation Notes -

Mitochondria revisited o Re-oxidation of redox cofactors, electron transport, and ATP synthesis occur within, on, and adjacent to the inner membrane o Oxidative phosphorylation takes place in the mitochondria o Outer membrane is freely permeable to small molecules and ions o Inner membrane is impermeable to most small molecules and ions (even protons, H+)  Contains respiratory electron carriers (complexes I-IV), ADP-ATP translocase, ATP synthase (F0F1), and other membrane transporters o Matrix contains:  Pyruvate dehydrogenase complex  Citric acid cycle enzymes  Fatty acid B-oxidation  Amino acid oxidation  DNA, ribosomes  Many other enzymes  ATP, ADP, Pi, Mg2+, Ca2+, K+  Many soluble metabolic intermediates o Endosymbiont theory – similar to bacteria (size, smaller ribosomes)  Similar size range  Protein- and RNA-encoding DNA  70S ribosomes  Respiratory electron transport chains  Electron transport-coupled ATP synthesis  Evolutionarily related?

 

-

Bacteria = mitochondria; cyanobacteria (can perform photosynthesis) = chloroplasts Oxidative Phosphorylation

o

o

Respiratory re-oxidation of NADH and FADH2 

 NADH + H+ + 1/2O2  NAD+ + H2O  Oxygen is reduced Energetics  Oxidation of NADH releases a tremendous amount of energy (too much for enzyme to handle) – so energy is transported to ATP (energy carrier)  NADH re-oxidation: highly exergonic (-220 kJ/mol)  1 mol NADH = >7 ATP  Electron transport – 10 protons transferred from matrix to intermembrane space for each NADH that is re-oxidized; 6 protons transferred for each FADH2 (from succinate oxidation) that is re-oxidized  NADH + 11 HN+ + ½ O2  NAD+ + 10 HP+ + H2O  Electron transport creates a disequilibrium  used later to drive the synthesis of ATP (either via chemical potential gradient or electrochemical potential gradient)  Electric potential is produced if a solute is a charged ion and its movement is not accompanied by a counterion  transport process is electrogenic (otherwise is electroneutral)  Electric potential difference affects the energetics of electrogenic transport  Proton-motive force (pmf) – energy stored in the electrochemical gradient  If C2 > C1 ([IMS]>[Matrix]), delta G is negative



 Energy gained from NADH re-oxidation is conserved in a proton gradient  Active transport of H+ across the inner membrane: NADH + 11 HN+ + ½ O2  NAD+ + 10 HP+ + H2O  Delta psi = voltage potential across membrane  In active mitochondria, delta psi is 0.15 – 0.2 V and delta pH is ~0.75 units  Energy required to transfer H+ across inner membrane: delta G = 20 kJ/mol of H+ o For 10 mol of transferred H+, 200kJ (90%) of the 220 kJ that are released by re-oxidation of a mole of NADH is conserved in the proton gradient  Exergonic (downhill) flow of electrons to O2 occurs through a series of redox cofactor within in the respiratory chain  Many cofactors are contained within several protein complexes imbedded in the inner membrane  Flavin nucleotide cofactors  Flavin Mononucleotide: FMN – oxidized, FMNH2 – reduced  Flavin Adenine Dinucleotide: FAD – oxidized, FADH2 - reduced Iron-sulfur proteins, ubiquinone, Q cycle  Iron-sulfur clusters  Only 1 iron in each Fe/S cluster changes its oxidation state 

o

 



Ex: Ferredoxin: Reduced state – 2Fe2+, 2Fe3+, Oxidized state – 1Fe2+, 3Fe3+ Ubiquinone (coenzyme Q) – highly lipophilic and is dissolved within the inner membrane

  

 Cytochromes  Heme is a prosthetic group of cytochromes o Electron transport chain complexes Chemiosmotic model for ATP synthesis ATP synthase, binding-change model Uncouplers and inhibitors of electron transport Nucleotide transporters and redox shuttles Total yield of ATP from glucose oxidation Regulation of ATP synthesis, energy change o

-

Ubiquinone – Q (fully oxidized); Semiquinone radical – ‘QH, Ubiquinol – QH2 (fully reduced) Long isoprenoid sidechain...