Lecture 19 Ch 21 ATP Synthesis Proton Motive Force hypothesis ATP synthase Compositions how it works P O ratio and the final ATP count Shuttle systems Uncouplers of oxidation phosphorylation 1 Oxidative Phosphorylation 2 Chemiosmotic Hypothesis By Peter Mitchell 1961 3 4 5 Racker and Stoeckenius Confirmed the Mitchell Model 6 ATP Synthase Complex V ATP ADP Pi 7 View of the ATP Synthase from the Top matrix side 8 Rotation of the subunit drives the conformational change of the subunits Subunit 1 L T O L T O Subunit 2 O L T O L T Subunit 3 T O L T O L http guweb2 gonzaga edu faculty cronk che mistry chem445 lectures cfm L 6 9 10 11 The F1 Portion of the ATP Synthase behaves as an ATPase when dissociated from the F0 subunit 12 13 14 Components of the proton conducting unit of ATP synthase H H H H H H H Asp61 Asp61 H H Matrix halfchannel 15 Proton path through the membrane Intermembrane space matrix Rotation driven by proton concentration 16 17 The ATP ADP translocase enables the exchange of cytoplasmic ADP for mitochondrial ATP ADP3 cytoplasm ATP4 matrix ADP3 matrix ATP4 cytoplasm 18 ATP ADP translocase On Innermembrane Homodimer 6 transmembrane domains Binding pocket mostly basic Antiporter 19 VDAC Voltage Dependent Anion Channel On Outermembrane Antiparallel Beta barrel Open at low or zero membrane potential Closed by 30 40 mV potential may be caused by Ca2 transport 20 Pi also need to be translocated to the matrix Generates H2O removing one H from Intermembrane space Adds one proton to the cost of synthesizing each ATP H2 O H 21 Why does FADH2 generate less ATP than NADH2 ATP synthase 9 subunits uses 9 protons 3 ATP 3 protons ATP Import of 1 Pi uses 1 proton 1 Pi to make 1 ATP Need 4 protons to make 1 ATP 1 NADH 10 protons out 2 5 ATP The P O ratio 1 FADH2 6 protons out 1 5 ATP 22 ATP Yield per molecule of glucose Glycolysis P O 2 net ATP 2 NADH 3 ATP Pyruvate AcetylCoA 2 NADH 5 ATP TCA 2 ATP GTP 6 NADH 2 FADH2 Oxidative Respiration each NADH 2 5 ATP each FADH2 1 5 ATP 15 ATP 3 ATP Grand Total of ATP 30 Will vary between tissues 23 How are NADH molecules from Glycolysis moved to Inner Membrane 24 Cytosolic NADH can enter the ETC via the Glycerophosphate Shuttle This shuttle operates in the skeletal muscle and brain 25 Cytosolic NADH enters the ETC via the Malate Aspartate Shuttle aminotransferase aminotransferase This shuttle operates in the liver kidney and heart mitochondria 26 Aspartate Asp ketoglutarate oxaloacetate glutamate Glu 27 28 The rate of oxidative respiration is determined by the need for ATP 29 The energy charge regulates the use of fuels 30 Uncoupling Protein 1 UCP 1 thermogenin 31 Brown Fat and Ucp1 Brown fat Nonshivering thermogenesis More mitochondria Mitochondria have UCP1 High in hibernating animals UCP1 Mitochondrial uncoupling protein aka Thermogenin Found in brown adipose tissue Increases permeability of Innermembrane 32 Non physiological chemical uncouplers 2 4 dinitrophenol DNP H H H H H 33
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