2/22/151Biochemistry401Lecture 21 Transporting Reducing Equivalents into the Mitochondrial MatrixOxidative Phosphorylation Overview: Electron Transport Chain (ETC)Integral membrane electron carriers Mobile electron carriers Following electrons through the electron transport chainCytochrome cComplex IVHow do reducing equivalents get from the cytoplasm into the mitochondrial matrix? Glycerol 3-phosphate Shuttle!1. Reduction of DHAP to Glycerol-3P 2. Reduction of FAD to FADH2 3. Reduction of MT e- carrier Q to QH Mobile inner mitochondrial membrane e- carrier Q: Ubiquinone(oxidixed).QH2: Ubiquinol (reduced)2/22/152Aspartate amino transferaseMT Malate dehydrogenaseMT Aspartate amino transferaseC Malate dehydrogenaseC Malate-Aspartate Shuttle!1) IN Cyto,OAA reduced to Malate - Malate Dehydrogenasecyto 2) Malate transported into MT 3) IN MT, Malate oxidized to OAA - Malate DehydrogenaseMT 4) IN MT, Glu is deaminated to make α-KG, NH3 group from Glu is transferred to OAA to make Asp - Aspartate AminotransferaseMT 5) Aspartate & α-KG transported to Cyto, 6) IN Cyto, Asp deaminated,makes OAA, NH3 group from Asp is transferred to α-KG to make Glu. -Aspartate AminotransferaseCyto(Glu transported into MT) 1 2 3 4 5 5 6 6 NOTES to Help you (no audio) α-Ketoglutarate NH3+ Aspartate Oxaloacetate Glutamate NH3+ Aspartate Amino Transferase2/22/1534C 5C 3C α α -!-!-!-!4C 5C 3C α α Amination changes these alpha keto acids to alpha amino acids!-!-!-!-!-!α Can you name these amino acids? !-O -O α α ________!________!________!NADH FADH2 : Glycolysis Fatty Acid Catabolism TCA Cycle NADH and FADH2 carriers of electrons with high transfer potential. Electrons are transferred and energy released during this transfer can be used to do work. : NADH FADH2 Other e- carriers e - Carrier 2e- energy energy Lowest electron transfer potential 1/2O2 energy Highest electron transfer potential2/22/154 Electron transfer potential can be quantified through the use of the expression: ∆E´0 This term refers to a molecule’s reduction potential. These two terms are interrelated this way: ∆G˚´ = - nF∆Ε´0 n = number of electrons F = Farraday’s constant (96.48 kJ mol-1 V-1) Highest: NADH FADH2 Other e- carriers e - Carrier 2e- energy Lowest electron transfer potential 1/2O2 energy The more negative the E´o, the greater the electron-transfer potential of the reductant and the greater the tendency to donate electrons. The more positive, the greater the tendency to accept electrons. 1. 1/2 O2 + NADH + H+ ⇄ H2O+ NAD+ 2. 1/2 O2 + 2H + 2e- ⇄ H2O Ε´0 = + 0.82V 3. NAD++ H++ 2e- ⇄ NADH Ε´0 = - 0.32V 4. NADH ⇄ NAD+ + H++ 2e- Ε´0 = + 0.32V Solve for ∆G˚´for each half-reaction ∆G˚´ = - nF∆Ε´0 Rxn 2: ∆G˚´ = -2 (96.48kJmol-1 V-1)(+0.82 V) = -158.23 kJmol-1 Rxn 4 ∆G˚´ = -2 (96.48kJmol-1 V-1)(+0.32 V) = - 61.8 kJ/mol-1 Sum 2 & 4:∆G˚´=-158.23 kJmol-1 - 61.80 kJmol-1 = - 220.03 kJmol-1 3 2 Flipped,so flip sign2/22/1553 Electron carriers in ETC Complex I Complex II Complex III Complex IV Glycerol 3-phosphate Shuttle FADH FADH e- H+ H+ H+ Cytochrome c H2O 1/2O22/22/156Fully oxidized Fully reduced Coenzyme Q10 Ubiquinone/ubiquinol have a long hydrocarbon tail!Which one is this? !Ubiquinone or ubiquinol?!e- H+ H+ H+ Cytochrome c H2O 1/2O22/22/157Histdine with a tyrosine adduct Oxygen is held in place as a peroxide bridge between an iron and copper metal ion Addition of 2 protons, 2 electrons Yields 2 hydroxyl groups Additional 2 protons, 2 electrons releases 2 H2O Complex I: NADH-Q oxidoreductase (NADH dehydrogenase) Accepts e- from NADH passes e- to ubiquinone Pumps protons into intermembrane space Complex III: Q-cytochrome c oxidoreductase Accepts e- from ubiquinol Passes e- to cytochrome c Pumps protons into intermembrane space Complex IV Cytochrome c oxidase accepts e- from cytochrome c Passes e- to molecular oxygen Pumps protons into intermembrane space Complex II: Succinate-Q reductase (succinate dehydrogenase) (same enzyme as in TCA cycle) Accepts e- from FADH2 passes e- to ubiquinone to form ubiquinol Does NOT pump protons into intermembrane space Integral membrane Electron carriers Mobile electron carriers Ubiquinone (fully oxidized), ubiquinol (fully reduced) (Co Enzyme Q) Hydrophobic, travels within the inner membrane Accepts e- from: Complex I (Q-NADH oxidoreductase) Complex II (Succinate-Q reductase) Glycerol 3-Phosphate Shuttle carries e- to Complex III (Q-cytochrome-c oxidoreductase) Cytochrome c Hydrophilic, travels in the intermembrane space Accepts electrons from Complex III (Q-cytochrome-c oxidoreductase) Carries e- to Complex IV (Cytochrome c oxidase)2/22/158• FMN • Iron-sulfur centers • Iron-containing cytochromes • Coper-containing cytochromes • Copper-containing centers Iron-sulfur centers Iron- and copper-containing cytochromes Copper-containing centers This is the end of Lecture 21. !Have a great
View Full Document
Unlocking...