Lipids PDF

Lipids Caner Geyik [email protected] HSF101 Learning Objectives  Explain structural properties of lipids  Explain the roles of lipids  Classify lipids  Recognize fatty acids  Explain lipid digestion and absorption  Recognize steroids  Classify lipoproteins  Explain fatty...

Lipids Caner Geyik [email protected] HSF101 Learning Objectives  Explain structural properties of lipids  Explain the roles of lipids  Classify lipids  Recognize fatty acids  Explain lipid digestion and absorption  Recognize steroids  Classify lipoproteins  Explain fatty acid catabolism (beta oxidation)  Explain fatty acid synthesis  Lipids Lipids are defined as water-insoluble (hydrophobic) molecules that are highly soluble in organic solvents Hydrophilic Hydrophobic  Lipids Not all lipids are the same ! Polar side Non-polar side  Roles of Lipids Widely used to store energy (needs less water than CHOs) Key components of membranes Elements in signaling (hormones, signal molecules) Thermal insulation  Types of the Lipids Sphingolipids Fatty acids Waxes Terpenes Phospholipids Ceramides Steroids …and more Triacylglycerides Eicosanoids Lipids Most common biological important lipids  Fatty Acids Hydrocarbon chain Carboxylic acid  Fatty Acids 3 1 n β 2 ω α Fatty Acids  Glycerol Provides a base for fatty acids Other molecules can also bind C-1, 1st position C-2, 2nd position C-3, 3rd position Triacylglycerol Triacylglycerol = Triacylglyceride = Triglyceride TAG, TG Energy storage in adipose tissue Fatty acids + glycerol  Monoacylglycerol  Diacylglycerol  Triacylglycerol  Phospholipids Backbone: glycerol or sphingosine 1. Glycerophospholipids (Phosphoglycerides) 2. Sphingophospholipids (Phosphosphingolipids, Sphingomyelins)  Glycolipids Backbone: glycerol or sphingosine Blood Types Steroids  Hormones  Estradiol  Testosteron  Lipid digestion  Bile acids  Membrane  Cholesterol Steroid Hormones Metabolic Process of Lipids Obtained via Diet Digestion Absorption Transportation Digestion Milk, egg yolk and fats containing short chain Mouth fatty acids Activation of Von Ebner’s gland Secretion of lingual lipase Stomach Gastric lipase (requires Ca2+) Intestine Pancreatic lipase  Digestion Peristaltis, mechanical mixing Bile salts, detergent properties as they decrease the surface tension https://www.youtube.com/watch?v=jud8LN1Scfg&t=56s Digestion 1. TAG: 2-monoacylglycerol and free fatty acids 2. Cholesteryl esters: Cholesterol and free fatty acids 3. Phospholipids: Glycerylphosphoryl and free fatty acids Absorption The products of lipase digestion form micelles for absorption by the intestinal cells.  Free fatty acids  Free cholesterol  2-monoacylglycerol  Fat soluble vitamins  (A, D, E, and K)  Bile salts: Terminal ileum / (5% excreted) Absorption and Transport In the cells of the intestine, triacylglycerols are re-formed and packaged into lipoprotein particles called chylomicrons for transport in the lymph system and the blood. Lipoproteins  Chylomicrons  Very low density lipoproteins (VLDL)  Low density lipoproteins (LDL)  High density lipoproteins (HDL) Lipoproteins  Lipoprotein Structure Amphipathic Lipid solubility Lipid transport Lipoproteins Lipid Catabolism Fatty acid Glycerol  Even number of carbon atoms → Acetyl-CoA G 3-P DHAP  Odd number of carbon atoms → Acetyl-CoA + Propionyl-CoA Succinyl-CoA Fatty Acid Oxidation 1. Activation  CoA is added to structure 2. Transport to Mitochondria  Carnitine binding 3. β-oxidation  Acetyl CoA units leave the structure Fatty Acid Oxidation 1. Activation 1 ATP is used but 2P groups are separated. Expenditure is 2 ATP energy 2. Transport Fatty Acid Oxidation 3. Beta oxidation A repetitive process that removes 2 carbon (as Acetyl-CoA) in every turn Every step produce: 1 NADH 1 FADH2 Example: Palmitic acid (16:0) oxidation  16 Carbons  2C will leave in every step Acetyl CoA 7 steps (7 NADH, 7 FADH2 formation) 8 Acetyl CoA is formed Fatty Acid Oxidation  Acetyl CoA molecules produced enter Acetyl CoA TCA Cycle  1 palmitic acid:  8 Acetyl CoA  7 NADH  7 FADH2  = 129 ATP  Example: Margaric acid (17:0) oxidation  ODD NUMBER ALERT ! Propionyl CoA (3C)  Difference from (16:0) Succinyl CoA (4C)  7 Acetyl CoA (1 less)  1 propionyl CoA (Succinyl-CoA formation, -1 ATP)  Succinyl CoA in TCA gives less energy compared to Acetyl Energy Yield: CoA in TCA 16C > 17C Fatty Acid Synthesis  Occurs in the cytosol  Uses Acetyl CoA and NADPH as starting materials 3 Main Stages 1. Acetyl CoA Transport 2. Malonyl CoA Synthesis 3. Elongation of Fatty Acid Chain Fatty Acid Synthesis 1. Acetyl CoA Transport  Fatty Acid Synthesis 2. Malonyl CoA Synthesis Enzyme-biotin - Activated form of Acetyl CoA for HCO3 + ATP 1 synthesis ADP + Pi - Enzyme-biotin-CO2 Acetyl CoA Carboxylase O ll 2 Coenzyme: Biotin CH3-C-SCoA Enzyme-biotin acetyl-CoA O - ll O2C-CH2-C-SCoA malonyl-CoA Fatty Acid Synthesis 3. Elongation of Fatty Acid Chain Fatty Acid Synthesis 3. Elongation of Fatty Acid Chain Fatty Acid Synthesis omega-6 omega-3