Lipid Catabolism Lehninger Readings Chapter 17 pages 667 688 Lipids serve as a major source of cellular energy At the end of this section you should be able to describe the processes your body uses to extract energy from the lipids you consume and from lipids stored in your body Student Learning Objectives You should be able to 1 Tell the Big Picture story of how lipids are catabolized 2 Explain both in terms of cellular packaging kJ g dry weight and total energy why fatty acids are an important energy reserve in the human body 3 Describe the digestion and absorption of lipids including emulsification hydrolysis and transfer to the bloodstream 4 Describe the structure of chylomicrons and their role in transport of lipids 5 Describe the functions of dietary lipases hormone sensitive lipase and lipoprotein lipase in metabolism of fatty acids 6 Compare and contrast the degradation and transport of dietary triacylglycerols and triacylglycerols in adipose tissue 7 Describe how glycerol from triacylglycerol is catabolized 8 Explain how fatty acids are activated and transported into the mitochondria 9 Connect oxidation to other catabolic processes used to generate energy 10 Describe the steps enzymes cofactors and metabolic intermediates involved in the oxidation of fatty acids their localization and the regulation of the process 11 Compare and contrast oxidation with the oxidation of succinate to oxaloacetate in the TCA cycle 12 Calculate the number of ATPs produced from the degradation of saturated and unsaturated even number fatty acid 13 Know the special requirements for the oxidation of unsaturated and oddnumber fatty acids 14 Describe oxidation of fatty acids in peroxisomes 15 Compare and contrasts oxidation of fatty acids in peroxisomes and mitochondria 16 Describe ketone bodies and the intermediates and reactions involved in their metabolism 17 Explain the purpose of ketone bodies in metabolism including sites of production and utilization 18 Explain the relationship between acetyl CoA and ketone bodies 19 Describe ketosis and relate this to the fact that humans lack the glyoxylate cycle 20 Explain why starvation increases the production of ketone bodies and their use as an energy source Page 1 Lipid Catabolism 1 Tell the Big Picture story of how lipids are catabolized 2 Explain both in terms of cellular packaging kJ g dry weight and total energy why fatty acids are an important energy reserve in the human body The structural physical chemical properties of each drive its functions Building block Storage in humans amino acids monosaccharides fatty acid Energy No specific storage form 17 kJ g Glycogen which is hydrated 16 kJ g Lipid Droplets which are anhydrous 38 kJ g None nucleotides Energy storage in lipids Oxidation State of Carbon Storage Form Chemical Reactivity Page 2 3 4 5 Lipid Catabolism Describe the digestion and absorption of lipids including emulsification hydrolysis and transfer to the bloodstream Describe the structure of chylomicrons and their role in transport of lipids Describe the functions of dietary lipases hormone sensitive lipase and lipoprotein lipase in metabolism of fatty acids Figure 17 1 Lipid digestion absorption and transport in mammals Bile salts Intestinal lipases Absorption TAG Synthesis Chylomicrons Structure Function Figure 17 2 Lipoprotein lipases Page 3 Lipid Catabolism 6 Compare and contrast the degradation and transport of dietary triacylglycerols and triacylglycerols in adipose tissue Mobilization of TAGs from adipose tissue Lipid droplets structure Regulation Perilipin Figure 17 3 Activation and Role of Lipases 7 Describe how glycerol from triacylglycerol is catabolized Glycerol Metabolism Recycling to make glycerolipids Serum albumin Conversion to a glycolytic intermediate for energy ATP Glycerol Figure 17 4 NAD ADP Glycerol Kinase L Glycerol 3phosphate NADH Glycerol Phosphate Dehydrogenase Dihydroxyacetone phosphate Page 4 Lipid Catabolism Fatty Acid Catabolism Activation by fatty acyl CoA synthetase Mechanism Energetics 2 high energy phosphate bonds 2 ATP Equivalents used per fatty acid activated Figure 17 5 Page 5 Lipid Catabolism 8 Explain how fatty acids are activated and transport into the mitochondria Fatty Acid Catabolism Carnitine Shuttle Overall purpose Carnitine Acyltransferase I Acyl carnitine Carnitine Transporter Carnitine Acyltransferase II Regulation Figure 17 6 Page 6 9 Lipid Catabolism Connect oxidation to other catabolic processes used to generate energy Fatty Acid Catabolism Overview of Fatty Acid oxidation Oxidation of the carbon Removal of Acetyl CoA 2 carbons Figure 17 7 Oxidation of Acetyl CoA by the TCA cycle Page 7 Lipid Catabolism 10 Describe the steps enzymes cofactors and metabolic intermediates involved in the oxidation of fatty acids their localization and the regulation of the process Fatty Acid Catabolism The 4 steps in oxidation Dehydrogenation oxidation Hydration Dehydrogenation oxidation Figure 17 8 Thiolysis 11 Compare and contrast oxidation with the oxidation of succinate to oxaloacetate in the TCA cycle Figure 16 7 See also Figure 17 9 Compare with TCA cycle Page 8 Lipid Catabolism 12 Calculate the number of ATPs produced from the degradation of saturated and unsaturated even number fatty acid Fatty Acid Catabolism Repeating the four steps Figure 17 8 Start with palmitate How many rounds of oxidation ATP yield How many FADH2 and NADH H are produced during each round How many FADH2 and NADH H produced by complete oxidation How many acetyl CoA are produced How many FADH2 and NADH H and GTP are produced by oxidation of 1 acetyl CoA by the TCA cycle How many FADH2 and NADH H and GTP are produced by oxidation of all the acetyl CoA from oxidation of palmitate How many FADH2 and NADH H and GTP are produced by complete oxidation of palmitate by oxidation and the TCA cycle P O for FADH2 is 1 5 and NADH H is 2 5 How many ATP are produced by complete oxidation of palmitate don t forget to subtract 2 ATP for activation of palmitate by Acyl CoA synthetase Page 9 Lipid Catabolism 13 Know the special requirements for the oxidation of unsaturated and odd number fatty acids Fatty Acid Catabolism Monounsaturated Fatty Acids Cis Trans Isomerization Figure 17 10 ATP Production Page 10 Lipid Catabolism Fatty Acid Catabolism Polyunsaturated Fatty Acids 3 2 Isomerization Reduction NADPH donates 2 e s 3 2 Isomerization ATP production Figure 17 11 Page 11 Lipid Catabolism Fatty Acid Catabolism Odd chain Fatty Acids