Lipid Metabolism PDF

LIPID METABOLISM BIOCHEMISTRY  AGENDA o DEFINITION o DIGESTION AND ABSORPTION OF LIPIDS o LIPID METABOLISM PATHWAY o SUMMARY WHAT ABOUT IT?? Lipids are essential in overall cellular metabolism; not only because they are present in every cell but they present an energy rich fuel that...

LIPID METABOLISM BIOCHEMISTRY  AGENDA o DEFINITION o DIGESTION AND ABSORPTION OF LIPIDS o LIPID METABOLISM PATHWAY o SUMMARY WHAT ABOUT IT?? Lipids are essential in overall cellular metabolism; not only because they are present in every cell but they present an energy rich fuel that can be stored in adipose tissue. CAMEL’S HUMP Camel can go on for a long time without eating or drinking because they store rich fat in their humps, by which be converted into energy. LIPID METABOLISM This refers to the process of digestion, absorption, synthesis, and decomposition of fats in living organisms. Sciencedirect.com  98% of total dietary lipids are FOOD triacylglycerols (fats and oils) BOLUS CCK PANCREATIC LIPASE HYDROLYSIS HCL GASTRIC LIPASE MICELLE CHYME Chylomicron Lymphatic System Bloodstream TRIACYLGLYCEROL (TAG) STORAGE o Adipocyte is a triacylglycerol-storing cells o Adipose tissue is a tissue containing large numbers of adipose cells/adipocytes TRIACYLGLYCEROL MOBILIZATION Triacylglycerol mobilization is the hydrolysis of triacylglycerols stored in adipose tissue, followed by release into the bloodstream of the fatty acids and glycerol so produced. GLYCEROL METABOLISM o During triacylglycerol mobilization, one molecule of glycerol is produced for each triacylglycerol completely hydrolyzed Triacylglycerol  Pyruvate Oxidation Krebs Cycle Portion of Glycolysis Oxidative Phosphorylation OXIDATION OF FATTY ACIDS There are three parts to the process by which fatty acids are broken down to obtain energy. o The fatty acid must be activated by bonding to coenzyme A. o The fatty acid must be transported into the mitochondrial matrix by a shuttle mechanism. o The fatty acid must be repeatedly oxidized, cycling through a series of four reactions, to produce acetyl CoA, FADH2, and NADH PART I: BONDING TO COENZYME A o The fatty acid must be activated by bonding to coenzyme A. Location: Outer mitochondrial membrane Difference between Acyl CoA and Acetyl CoA Two-carbon chain PART II: FATTY ACID TRANSPORT o The fatty acid must be transported into the mitochondrial matrix by a shuttle mechanism. The acyl group is transferred to a carnitine molecule, which carries it through the membrane. The acyl group is then transferred from the carnitine back to a CoA molecule PART III: REACTIONS OF THE B-OXIDATION PATHWAY o The fatty acid must be repeatedly oxidized, cycling through a series of four reactions, to produce acetyl CoA, FADH2, and NADH For a saturated fatty acid, the b-oxidation pathway involves the following functional group changes at the b carbon and the following reaction types. PART III: REACTIONS OF THE B-OXIDATION PATHWAY o The fatty acid must be repeatedly oxidized, cycling through a series of four reactions, to produce acetyl CoA, FADH2, and NADH For a saturated fatty acid, the b-oxidation pathway involves the following functional group changes at the b carbon and the following reaction types. STEP 1: REACTIONS OF THE B-OXIDATION PATHWAY o First Dehydrogenation. Hydrogen atoms are removed from the a and b carbons, creating a double bond between these two carbon atoms. FAD is the oxidizing agent, and a FADH2 molecule is a product STEP 2: REACTIONS OF THE B-OXIDATION PATHWAY o Hydration. A molecule of water is added across the trans double bond, producing a secondary alcohol at the b- carbon position. Again, the enzyme involved is stereospecific in that only the L-hydroxy isomer is produced from the trans double bond. STEP 3: REACTIONS OF THE B-OXIDATION PATHWAY o Second Dehydrogenation. Removal of two hydrogen atoms converts the b-hydroxy group to a keto group, with NAD+ serving as the oxidizing agent. The required enzyme exhibits absolute stereospecificity for the L isomer. STEP 4: REACTIONS OF THE B-OXIDATION PATHWAY o Thiolysis. The fatty acid carbon chain is broken between the a and b carbons by reaction with a coenzyme A molecule. The result is an acetyl CoA molecule and a new acyl CoA molecule that is shorter by two carbon atoms than its predecessor. The new acyl CoA molecule (now shorter by two carbons) is recycled through the same set of four reactions again. This yields another acetyl CoA, a two-carbon shorter new acyl CoA, FADH2, and NADH. Recycling occurs again and again, until the entire fatty acid is converted to acetyl CoA. Thus the fatty acid carbon chain is sequentially degraded, two carbons at a time. : SUMMARY: THANK YOU END OF PART I