Essential Biochemistry - Lipid Metabolism I (PDF)

Essential Biochemistry 5th Edition Charlotte W. Pratt | Kathleen Cornely Chapter 17 Lipid Metabolism I  Objectives Describe the functions of lipids Describe the structure of lipid bilayer Describe properties of different lipoproteins and thei...

Essential Biochemistry 5th Edition Charlotte W. Pratt | Kathleen Cornely Chapter 17 Lipid Metabolism I  Objectives Describe the functions of lipids Describe the structure of lipid bilayer Describe properties of different lipoproteins and their function © 2014 John Wiley & Sons, Inc. All rights reserved.  Lipids have many functions Form lipid bilayer of cell – Glycerophopholipids, sphingolipids, cholesterol Source of energy – Triacylglycerol Signaling molecules – Arachidonic acid Hormones – Estrogen, testosterone, thyroxine, retinoate Vitamins – A, D, E, K © 2014 John Wiley & Sons, Inc. All rights reserved.  Characteristics of the Lipid Bilayer Fluid – No clearly defined geometry – Head groups move up, down – Hydrocarbon tails wave Asymmetric A lipid bilayer – Different lipids are found in each “leaflet” © 2014 John Wiley & Sons, Inc. All rights reserved. The lipid bilayer contains glycerophospholipids and sphingolipids O- O P O R O H O R H2C C CH2 H H HO C C CH2 O O Glycerol derived from CH NH derived from O C C O Serine Palmitate CH C O derived from Fatty acid Amphipathic derived from Fatty acid derived from other Fatty acid R=Choline =Phosphatidylcholine R=Ethanolamine=Phosphatidylethanolamine R = Phosphatidylcholine=Sphinogomyelin R=Glycerol=Phosphatidylglycerol R= Monosacharide=Cerebroside R=Serine=Phosphatidylserine R= Oligosaccharide=Ganglioside © 2014 John Wiley & Sons, Inc. All rights reserved.  The melting point of an acyl chain decreases as the degree of unsaturation increases and the length of acyl chain decreases. Double bonds kink the acyl chain. © 2014 John Wiley & Sons, Inc. All rights reserved. Triacylglycerols are a stored form of energy ATP © 2014 John Wiley & Sons, Inc. All rights reserved. Some Lipid Hormones OH H H H O Testosterone Copyright © 2018 John Wiley & Sons, Inc. All rights reserved. Arachidonate Conversion to Eicosanoid Signal Molecules Copyright © 2018 John Wiley & Sons, Inc. All rights reserved. © 2014 John Wiley & Sons, Inc. All rights reserved. © 2014 John Wiley & Sons, Inc. All rights reserved.  Lipoproteins © 2014 John Wiley & Sons, Inc. All rights reserved.  Approximately half of all deaths in the US are linked to atherosclerosis. Atherosclerosis – A slow progressive disease – Characterized by hardening of the arteries due to lipid accumulation in blood vessel walls © 2014 John Wiley & Sons, Inc. All rights reserved. Lipoproteins transport cholesterol and other fats. High-density Lipoprotein (HDL) Orange= Apolipoprotein Green= Lipid core containing cholesterol, phospholipids, cholesterol esters © 2014 John Wiley & Sons, Inc. All rights reserved.  Lipoproteins differ in their physicochemical properties © 2014 John Wiley & Sons, Inc. All rights reserved. Lipoprotein Function Illustrated Chylomicrons transport fats from intestines to tissues and VLDL transport cholesterol to triacylglycerols liver. from the liver to other tissues. Low-density High-density lipoproteins carry lipoproteins export cholesterol to the cholesterol from the tissues. tissues to the liver. © 2014 John Wiley & Sons, Inc. All rights reserved.  Lipoprotein Function Chylomicrons transport fats from intestines to tissues and cholesterol to liver. Very-low-density lipoproteins (VLDL) transport triacylglycerols from the liver to other tissues. Low-density lipoproteins 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.” © 2014 John Wiley & Sons, Inc. All rights reserved.  Lipid Metabolism In Context Triacylglycerols contain fatty acids attached to a glycerol backbone. Fatty acids are broken down into 2C and 3C intermediates that feed into the citric acid cycle. © 2014 John Wiley & Sons, Inc. All rights reserved. © 2014 John Wiley & Sons, Inc. All rights reserved. © 2014 John Wiley & Sons, Inc. All rights reserved. © 2014 John Wiley & Sons, Inc. All rights reserved. © 2014 John Wiley & Sons, Inc. All rights reserved.  Summary Lipids serve many Many hormones are functions lipid derived. – Lipid bilayer, energy, Lipid signaling signaling molecules, molecules. hormones, and vitamins. Lipoproteins Lipid bilayer is fluid – Made of protein and and asymmetric. lipids – Glycerophospholipids – Transport lipids and fats and sphingolipids Good vs Bad TAGs are a rich Cholesterol source of energy. © 2014 John Wiley & Sons, Inc. All rights reserved.