Lipids I Fatty Acids A Straight hydrocarbon chain CH3 CH2 CH2 CH2 CH2 COOH 1 4 24 carbons long 2 14 or more C B Saturation 1 Saturated Fatty Acids a All C s are saturated with H s 2 Monounsaturated Fatty Acids a One double bond C C 3 Polyunsaturated Fatty Acids a Multiple C C bonds 1 C Hydrogenation 1 adding H s to an unsaturated fat to make is solid at room temperature 2 often used in commercially processed foods C C Cis C C C C C C Trans D Nomeclature How to name a fatty acid 1 count the number of C s 2 count the number of double bonds 3 name according to omega or alpha end E Essential Fatty Acids 1 Linoleic Acid 18 2 6 or 18 2 9 12 2 Linolenic Acid 18 3 3 or 18 3 9 12 15 2 II Eicosanoids A hormone like substance 1 modulation of a Blood pressure b Platelet aggregation B Families 1 prostacyclins 2 thromboxanes 3 leukotrienes C Synthesized from 1 Arachidonate Acid 20 4 6 2 Eicosatrienoic Acid 20 3 6 2 Eicosapentanoic Acid 20 5 3 overhead D Characteristics of Eicosanoids Omega 6 Eicosanoid family Site of synthesis Mode of action Prostacyclins Vascular endothelium Thromboxanes Platelets Leukotrienes Leukocytes Vasodilator platelet anti aggregation Vasoconstrictor platelet aggregation Vascular contraction inflammation Prostaglandins Endothelium of a variety of cells Vascular smooth muscle contraction or relaxation 3 III Triglycerides A Glycerol backbone B Three fatty acids IV Phospholipids A Glycerol backbone B One or more fatty acid C One phosphate V Glycolipids A lipid and carbohydrate 4 VI Sterols A Steroid nucleus B Cholesterol 1 bile acids Lipid Digestion I Lingual Lipase A Secreted at base of tongue B Stable at a low pH II Biliary Emulsification A Emulsification 1 dispersion of fat in an aqueous solution B Bile salt emulsifying agent 5 III Lipolysis Three main enzymes A Pancreatic Lipase B Cholesterol esterase C Lecithinase Lipid Absorption I Micelle Formation A Fatty elements and fat soluble vitamins surrounded by bile salts B C Bile salts absorbed in ileum and returned to liver via EHC II Inside the enterocyte A Long chain fatty acids 12 C and other fatty components B Reformation C TG s fatty components proteins D Short chain fatty 6 Lipoproteins Complexes which carry lipid products in the blood and lymph to various tissues I Chylomicron A Formation lipids 1 synthesis in enterocytes from exogenous B Composition 1 apoproteins A B C E 2 triglycerides 3 PL cholesterol 1 2 80 15 C Size 1 largest lipoprotein with lowest density 2 90 100 nm 7 D Function 1 transport exogenous triglycerides to tissues 2 Lipoprotein Lipase LPL a Hydrolyzes TG to free fatty acids and glycerol E Chylomicron remnant 1 remains after TG hydrolysis 2 taken up by hepatocytes II Very Low Density Lipoprotein A Formation 1 synthesized in liver 2 released into blood B Composition 1 Apoproteins B C 2 Triglyceride 3 Cholesterol 4 Phospholipids 8 50 20 20 C Size 30 90nm D Function 1 transports endogenous lipid from liver to extra hepatic tissues 2 Lipoprotein Lipase LPL a Hydrolyzes TG to free fatty acids and glycerol 8 III Intermediate Density Liporotein A Formation 1 from VLDL after TG hydrolysis 2 transient very short lived B Function 1 formed into LDL after TG hydrolysis via LPL IV Low Density Lipoprotein A Formation 1 from IDL after TG hydrolysis B Function 1 delivers cholesterol to non hepatic tissues 2 uptake via receptor mediated endocytosis C Composition 1 apoproteins B 100 2 triglyceride 3 cholesterol 4 phospholipids D Size 20 25 nm 21 9 50 23 9 E Receptor Mediated Endocytosis 1 Receptors located in clatharin coated pits 2 Receptors are specific for proteins LDL have apo B 100 3 LDL and receptor bind 4 Receptor and LDL complex internalized a Forms vessicle 5 vessicle fuses with lysosome 6 lysosome changes pH 7 ApoB degraded to amino acids 8 cholesterol released into cell 9 receptor returns to surface 10 Regulation a HMG CoA reductase activity 1 rate limiting enzyme for cholesterol synthesis 2 more cholesterol in cell b LDL receptor synthesis 1 if cholesterol levels in cell are high will decrease LDL receptor synthesis V High Density Lipoproteins A Formation Liver and Intestine B Composition 1 apoprotein A C D E 2 triglyceride 3 cholesterol 4 phospholipid C Size 5 25 nm 50 3 20 30 10 D Function tissues 1 removal of cholesterol from non hepatic 2 Lecithin cholesterol acyltransferase LCAT a Allows HDL to pick up cholesterol from cell membranes or from other lipoproteins b Apo A1 binds to LCAT receptor Cholesterol I Synthesis A a little more than of all cholesterol in body is synthesized B Location 1 liver 10 2 intestine 10 II Regulation of cholesterol synthesis A HMG CoA reductase Activity 1 rate limiting enzyme 2 reduced by a Cholesterol b Fasting c d B Dietary cholesterol 1 dietary cholesterol 2 dietary cholesterol 3 we eat 600 mg d RDA 300mg d 11 III Transportation A HDL high density lipoprotein transports cholesterol from tissues to liver B LDL low density lipoprotein transports cholesterol from liver to tissues IV Functions A Cell membranes 1 maintains fluidity B Steroid Hormones 1 testosterone 2 androgens 3 estrogen 4 progesterone Bile I Composition A 82 water B 12 bile salts C 4 phospholipids D 0 7 free cholesterol E Electrolytes F Bile pigments 1 biliverdin and bilirubin II Volume 12 III Synthesis A Hepatocytes 1 CCK 2 secretin 3 gastrin B Sent to gall bladder C CCK stimulates release from gall bladder 1 contraction of gall bladder 2 through sphincter of Oddi IV Function A lipid emulsification B essential for fat digestion Fatty Acid Synthesis I Synthesis A Glucose primary substrate B Membrane permeability 13 II Fatty Acid Synthase A Enzyme complex 1 thioesterase 2 acyl carrier protein 3 ketoacyl reductase 4 enoyl reductase 5 hydratase 6 transcyclase 2 7 ketoacyl synthase B Active Complex 1 dimer of 2 identical polypeptide monomers 2 monomers connected by 2 disulfide bonds III Desaturation A Addition of double bonds H C H H C H NADPH H 2H2O NADP H C H H C H H C H C H Desaturase H C H C H H C H H C H H C H H C H 14 B Essential Fatty acids 1 lack enzymes 12 and 15 desaturase which add bonds past 9 position 2 18 2 9 12 3 18 3 9 12 15 Oxidation I Breaking down long chain fatty acids for energy II Energy A Even chain B Odd chain Notes on Overheads Ketones After oxidation there are two pathways for energy production from fatty acids 1 Krebs cycle review cycle 2 Ketone production 15 I Ketone bodies 1 acetoacetate 2 hydroxybutarate 3 acetone II Energy Palmitate Palmitoyl CoA Acetyl CoA Krebs Acetoacetate
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