7/12/15&1&Biochemistry401Lecture 22 ATP SynthesisUncouplers of Oxidative PhosphorylationPoisons of Oxidative Phosphorylation Chemiosmotic potential causes protons to flow flow back into the mitochondrial matrix, which turns a turbine-like molecular motor which helps to synthesize ATP. + + + + + - - - - - - Energy released during electron transfer can be used to pump H+ into into the inter-membrane space, creating a proton concentration gradient, and electrical potential across the inner membrane. This is called chemiosmotic potential. Fo F1 http://www.pdb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb72_1.html Intermembrane Space Matrix7/12/15&2&http://www.pdb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb72_1.html Stationary hexameric ringCentral Shaft C-Ringγ !Central !Shaft!α3,β3 !Hexameric Ring!7/12/15&3&Neither half channel spans the membrane, but instead abuts a c subunit. Rotation depends on interactions between subunits c and a. H+ ATP ADP +Pi Intermembrane space: High [H+] Matrix: Low [H+] H+ Protons move down their concentration gradient, powering ATP- synthase. +++++ - - - - - - - Intermembrane Space Matrix Aspartate: in a proton-poor environment Aspartic acid: Proton-rich environment Aspartic acid is neutral: Can enter hydrophobic membrane c-Ring Asp7/12/15&4&C-Ring Asp Aspartate: in a proton-poor environment, negative charge Aspartic acid: in a proton-rich environment, neutral in charge Aspartic acid can enter the hydrophobic membrane7/12/15&5&β-subunit is the site of ATP synthesis and has 3 conformations: O = Open (Step 1) T = Tense (Step 2) L = Loose (Step 3) In the loose conformation, ADP and Pi are bound (but do not react) In the Tense conformation, ADP and Pi react to form ATP. In the open conformation, ATP is released.7/12/15&6&The subunit highlighted in yellow is in the tense conformation because of its interaction with the central γ-subunit. ATP is synthesized. With rotation of the γ- subunit 120 degrees clockwise, the subunit highlighted in yellow is open, a conformation that allows ATP release. ATP is released, allowing another ADP and Pi to bind. ATP ADP + Pi ATP Step one7/12/15&7& I III IV ATP-synthase Cyt c7/12/15&8&Uncoupler I III IV I III IV ATP-synthase Cyt c CO and H2S ATP-synthase Blocked by oligomycin – (Azide), I III IV ATP-synthase Blocked by oligomycin Rotenone: Insecticide Amytal: Barbiturate Antimycin: Antibiotic CO, and H2S Cyanide, Azide, H2S (Sewer gas) and CO Oligomycin: Antibiotic – (Azide),7/12/15&9& To help you: P/O ratio ATP produced per ½O2 reduced, yielding H2O NADH = ~ 2.5 FADH2 = ~ 1.5 + + + + + - - - - - - H+ H+ H+ H+ H+ I III IV ATP-synthase Cyt c Net molecules of ATP from Glycolysis = 2/ molecule of glucose7/12/15&10&Total molecules of ATP from Glycolysis = 2/ molecule of glucose Total molecules of ATP from TCA cycle = 2 / molecule of glucose Net molecules of ATP from Glycolysis = 2/ molecule of glucose Total molecules of ATP from TCA cycle = 2 / molecule of glucose 26 Varies w/shuttle Glycerol 3-P = 30, Malate–Aspartate = 32 4 This marks the end of Lecture 22. !Have a super
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