ATP Synthesis Biochem 4511 Figures Essential Biochemistry 3rd Ed Pratt and Cornely Principles of Biochemistry 5th Ed Moran et al Fundamentals of Biochemistry 2nd Ed Voet Voet and Pratt ATP Synthase Rotation a blue b green g purple Proton transport down the gradient rotates the subunit as the c subunits turn 8 protons round The subunit changes the conformation of the 3 3 complex F1 as it rotates This change in conformation of the dimer is coupled to ATP synthesis Conformational Change Synthesizes ATP The subunits form three different conformations O open T tight L loose ADP and Pi bind to the open conformation ATP is formed in the tight conformation ATP is released in the open conformation 3ATP molecules generated round Quantifying Oxidative Phosphorylation The P O ratio describes the stoichiometry of oxidative phosphorylation P O ratio is the number of ATP molecules produced per oxygen atom reduced Theoretical 3 7 2 5 NADH in vivo Theoretical 2 2 1 5 NADH in vivo P O ratios are based on the mechanical movement of ATP synthase and linked to the number of protons translocated per electron The rate of oxidative phosphorylation depends on the rate of fuel catabolism Oxidative phosphorylation is regulated by the availability of reduced cofactors NADH and QH2 produced by other metabolic processes ADP ATP Translocase ATP 4 and ADP 3 are charged molecules so they cannot freely diffuse across the mitochondrial membrane Transport of ATP from the matrix is coupled to transport of ADP into the matrix Pi transport uses the H gradient across the membrane created by the proton pumps of the ETC Protonmotive Force can also Produce Heat Body heat can be produced when protons run back along the gradient without producing ATP An alternative return route for the protons exists through an uncoupling protein in the inner membrane Thermogenin Thermogenin allows the return of protons to the matrix and the protonmotive force energy is released as heat Brown Fat 1 High content of energy molecules fatty acids 2 Higher number of mitochondria compared to typical cells 3 Mitochondria also have a higher than normal concentration of thermogenin in their inner membrane ATP Synthase Proton translocation drives the rotation of a portion of ATP synthase Rotation induced conformational changes allow ATP synthase to bind ADP and Pi to phosphorylate ADP and to release ATP The supply of reduced cofactors determines the rate of oxidative phosphorylation Regulation of ATP Synthesis ATP synthase cannot operate in the absence of ADP The proton gradient is not utilized when ATP is abundant and ADP is scarce Under these conditions electron flow along the ETC is also inhibited which leads to accumulation of reduced NADH and FADH2 This leads to inhibition of the TCA cycle How The Inhibition of the TCA cycle adds to inhibition of Glycolysis How Lipid Metabolism Biochem 4511 Figures Essential Biochemistry 3rd Ed Pratt and Cornely Principles of Biochemistry 5th Ed Moran et al Fundamentals of Biochemistry 2nd Ed Voet Voet and Pratt Artherosclerosis Approximately half of all deaths in the US are linked to atherosclerosis A slow progressive disease Characterized by hardening of the arteries due to lipid accumulation in blood vessel walls High levels of HDL and low levels of LDL VLDL help to prevent progress of disease Lipoprotein Function Illustrated High density lipoprotein HDL Protein orange Lipid core containing cholesterol phospholipids cholesteryl esters green Lipoprotein Function Chylomicrons transport fats from intestines to tissues Very low density lipoproteins VLDL transport triacylglycerols from the liver to other tissues Low density lipoproteins LDL carry cholesterol to the tissues LDL levels should be relatively low LDL is commonly referred to as bad cholesterol High density lipoproteins export cholesterol from the tissues to the liver HDL levels should be relatively high HDL is commonly referred to as good cholesterol Lipid Composition of Lipoproteins Regulating your lipid consumption is extremely important for maintaining a healthy level of lipoproteins in your bloodstream Accumulation of lipid deposits in your blood vessels leads to atherosclerosis and heart disease Lipid Metabolism Overview Triacylglycerols contain fatty acids attached to a glycerol backbone Glycerol can be converted to glycerol 3 phosphate Fatty acids are broken down into 2 and 3 carbon intermediates that feed into the citric acid cycle Triacylglycerols are the Primary Source of Fatty Acids to be Metabolized Fatty acids to be metabolized are first hydrolyzed from triacylglycerides by lipoprotein lipase Acyl CoA Fatty Acids are Activated Before Degradation Fatty acids to be degraded first react with ATP to yield the AMP fatty acid product and pyrophosphate AMP is displaced from the fatty acids by coenzyme A yielding a thioester bond containing acyl CoA Mitochondrial Import of Acyl CoA Acyl groups are transferred across the membrane via carnitine Acyl CoA is then degraded into multiple acetyl CoA molecules Oxidation is a Spiral Process There are four reactions in each round of oxidation but the enzymes isozymes may be different due to different chain length Each round produces acetyl CoA ubiquinol QH2 and NADH Oxidation Oxidation Oxidation Generates Significant ATP One round of oxidation produces one molecule of acetyl CoA one ubiquinol QH2 and one NADH A total of 14 ATP molecules can be generated from every two carbons in a fatty acid Fatty Acid Degradation Oxidation Fatty acids to be degraded are linked to coenzyme A and transported into mitochondria There are four reactions in each round of oxidation that produce acetyl CoA ubiquinol QH2 and NADH Additional enzymes are necessary for breaking down unsaturated fatty acids Fatty acids with an odd number of carbons yield propionyl CoA that is ultimately converted to acetyl CoA Unsaturated Fatty Acids with cis Bonds Require Additional Processing 3 round of b oxidation Enoyl CoA isomerase converts a cis 3 4 double bond to a trans 2 3 double bond so that oxidation can proceed When linoleate is degraded another double bond blocks oxidation 2014 John Wiley Sons Inc All rights reserved Oxidation of Odd Chain Fatty Acids Yields Propionyl CoA Succinyl CoA is further processed through the TCA cycle Breakdown of Propionyl CoA 2014 John Wiley Sons Inc All rights reserved Outline of Fatty Acid Anabolism Fatty acid synthesis begins with the carboxylation of acetyl CoA in the cytosol Fatty acid synthase catalyzes