HUN3224 Exam 3 Review Farrell Lipids Fatty Acids o Straight hydrocarbon chain o CH3 CH2 CH2 CH2 CH2 COOH 1 4 24 carbons long 2 14 or more C nutritionally significant 3 Most are even of carbons Most fatty acids occurring in nature are even o Saturation Saturated fatty acids All C s are saturated with H s No double bonds C C Monounsaturated fatty acids One double bond C C Olive oil canola oil Polyunsaturated fatty acids Multiple double bonds Cis form is predominant Rule of thumb for oils chart saturated fatty acids are solid at room temperature most are animal fats except coconut palm etc Animal fats and the tropical oils of coconut and palm are mostly saturated o Coconut butter beef tallow palm oil lard Some vegetable oils such as olive and canola are rich in monounsaturated fatty acids o Olive oil canola oil peanut oil Many vegetable oils are right in polyunsaturated fatty acids o Safflower sunflower corn soybean cottonseed Adding H s to an unsaturated fat to make it solid at room temperature Ex Crisco Often used in commercially processed foods Ex Crackers cookies snack cakes etc o Hydrogenation o Nomenclature CH3 omega or n end COOH alpha end or delta end How to name a fatty acid Count the number of C s Count the number of double bonds Name according to omega or alpha end o Double bonds are always 3 carbons apart o Delta end name every double bond o Omega end name only one double bond first one Tophat Question From image shown in class Is this 18 2 omega 5 or 18 2 omega 6 18 2 omega 6 o Essential fatty acids Linoleic acid 18 2 omega 6 or 18 2 delta 9 12 Alpha Linolenic acid 18 3 omega 3 or 18 3 delta 9 12 15 We lack the enzyme to add double bonds beyond delta 9 Eicosanoids o Hormone like substance Modulation of Blood pressure Platelet aggregation Immune system Nervous system Smooth muscle contraction o Families Prostacyclins Thromboxanes Leukotrienes o Synthesized from Arachidonate acid 20 4 omega 6 Eicosatrienoic acid 20 3 omega 6 Eicosapentoic acid 20 5 omega 3 o Look at eicosanoids diagram o Characteristics of eicosanoids Omega 6 Eicosanoid family Site of synthesis Prostacyclins Vascular endothelium Thromboxanes Platelets Leukotrienes Leukocytes Prostaglandins Endothelium of a variety of cells Mode of action Vasodilator platelet anti aggregation Vasoconstrictor platelet aggregation Vascular contraction inflammation Vascular smooth muscle contraction or relaxation Triglycerides o Glycerol backbone three carbon chain o Three fatty acids o Tophat Question Where are most of our triglycerides located Adipocytes Phospholipids o Glycerol backbone o One or more fatty acid o One phosphate Glycolipids o Lipid and carbohydrate Sterols note do not provide energy o Steroid nucleus o Cholesterol used to make Bile acids Steroidal sex hormones Adrenocortical hormones Vitamin D Cell membranes Lipid Digestion Lingual Lipase o Secreted at base of tongue o Stable at low pH o Efficient digestion of milk fat o Tophat Question Where do we use the majority of phospholipids in our body Infants Biliary emulsification o Emulsification Dispersion of fat in an aqueous solution Allows for lipase action o Bile salt emulsifying agent Lipolysis o Three main enzymes Pancreatic lipase Cholesterol esterase Lecithinase Lipid Absorption Micelle formation Look at pancreatic lipase and cholesterol esterase diagrams o Fatty elements and fat soluble vitamins surrounded by bile salts o Passive diffusion of fatty elements and vitamins at distal duodenum and jejunum Some in the ileum also except most of nutrients are already absorbed when it reaches there o Bile salts absorbed in ileum and returned to liver via Enterohepatic Circulation Inside the enterocyte phospholipids o Long chain fatty acids 12C other fatty components activated with enzyme A o Reformation of fatty components into triglycerides cholesterol esters and o TG s fatty components proteins all forms chylomicron Chylomicron is a lipoprotein protein lipid o Short chain fatty acids instead of putting the chylomicron you attach to albumin Albumin is protein that is made in liver carries products through the body including short chain fatty acids o Look at inside enterocyte diagram drawn in class o Tophat Question When we elongate a fatty acid using a desaturase we are changing it from an omega 3 to an omega 6 False Lipoproteins Complexes which carry lipid products in the blood and lymph to various tissues Every lipoprotein has same basic make up shown in picture o Ex Apoprotein phospholipids cholesterol TG CE o Tophat Question Chylomicrons are made from Fat we eat Chylomicron o Formation Synthesis in enterocytes from exogenous lipids Released in lymph o Composition Apoproteins A B C E Triglycerides PL cholesterol 1 2 80 15 Note percentages or size will not be asked on exam o Size o Function Largest lipoprotein with lowest density 90 100 nm Transport exogenous triglycerides to tissues Lipoprotein lipase LPL Hydrolyzes TG to free fatty acids and glycerol Free fatty acids and glycerol absorbed into tissues o Chylomicron remnant Remains after TG hydrolysis Taken up by hepatocytes via receptor mediated endocytosis Very Low Density Lipoprotein VLDL o Formation Synthesized in liver Released into blood o Composition Apoprotiens B C Triglyceride Cholesterol Phospholipids 8 50 20 20 o Size o Function 30 90 nm Transports endogenous lipid from liver to extra hepatic tissues Lipoprotein Lipase LPL Hydrolyzes TG to free fatty acids and glycerol Free fatty acids and glycerol absorbed into tissues Intermediate Density Lipoprotein IDL o Formation From VLDL after TG hydrolysis Transient very short lived o Function Formed into LDL after TG hydrolysis via LPL look at lipoprotein diagram shown in class o Tophat Question True or false Lipoprotein Lipase only functions with the VLDL and IDL False o Formation o Function o Composition also works with chylomicron remnant Low Density Lipoprotein LDL From IDL after TG hydrolysis Delivers cholesterol to non hepatic tissues Uptake via receptor mediated endocytosis Apoproteins B 100 Triglyceride Cholesterol Phospholipids 21 9 50 23 o Size 20 25 nm o Receptor mediated endocytosis Receptors located in clatharin coated pits Receptors are specific for proteins LDL have Apo B 100 LDL and receptor bind Receptor and LDL complex internalized Forms vessicle Vessicle fuses with lysosome Lysosome changes pH Apo B degraded to amino acids Cholesterol released into cell Receptor returns to surface Regulation HMG CoA reductase activity o Rate limiting
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