HUN3224 Study Guide for 3rd Exam Intro to Lipids Digestion and Absorption Know the concepts surrounding fatty acids saturation cis versus trans configurations nomenclature chain length essentiality Fatty acids Simplest of the lipids Straight hydrocarbon chain ending with COOH carboxyl group this makes a polar hydrophilic end and a nonpolar hydrophobic end Most of the calories from dietary fat come from fatty acids Saturation All of the carbons in the chain are linked to hydrogens saturated with Hs Monounsaturated MUFA 1 carbon carbon double bond is present in the chain Saturated SFA Polyunsaturated 2 carbon carbon double bonds are present Cis vs trans configurations Wherever there s a carbon carbon double bond there can be a cis or trans configuration Cis hydrogens are attached to the same side of the double bond bends the molecule making it U shaped Trans hydrogens are attached at opposite sides of the double bond gives it a more linear shape similar to saturated fatty acids the more double bonds in the molecule the stronger the bending effect Nomenclature Count the of C Count of double bonds Name according to alpha or omega end delta vs omega systems of notation Ex Linoleic acid Delta 18 2 9 12 a 18 represents total of carbon atoms b 2 repesents total double bonds present c 9 12 represents at what carbons the double bonds begin d For this system one starts counting the carbons from the COOH end of the fatty acid aka the alpha end Omega 18 2 6 or 18 2 n 6 a 18 repesents total of carbon atoms b 2 represents total double bonds present c 6 represents the carbon where the first double bond is located This takes into account that in a fatty acid double bonds are always separated by 3 carbons d For this system one starts counting the carbons from the CH3 end aka the omega end Chain length 4 24 carbons Essentiality These unsaturated fatty acids can t be synthesized in the body so we must ingest them through plant foods This is because we lack enzymes to make double bonds past 9 carbon in the chain this will be discussed in more detail under the Fatty Acid Synthesis section Linoleic acid 18 2 6 18 2 9 12 linoleic acid 18 3 3 18 3 9 12 15 From these we can make linolenic acid arachidonic acid Be able to name fatty acids I m not quite sure what this bullet means If she meant naming as in nomenclature see above If she meant to be able to list some fatty acids see this table from the book Know the functions and examples of eicosanoids sterols and phospholipids Eicosanoids Hormone like derivatives of fatty acids overall in charge of modulation of blood pressure platelet aggregation Family Mode of action Prostacyclins Vasodilator platelet anti aggregation Thromboxanes Vasoconstrictor platelet aggregation Leukotrienes Vascular contraction inflammation Prostaglandins Vascular smooth muscle contraction or relaxation the book makes no distinction between prostaglandins prostacyclins Sterols Cholesterol precursor for steroids in the body bile acids estrogens androgens progesterone adrenocortical hormones vitamin D of tissue cholecalciferol Phospholipids General functions cell membrane components anchoring proteins to surfaces of cell Lecithin aka phsphatidylcholine needed for eicosanoid synthesis membrane intracellular signaling act as second messengers in hormone stimulation Be able to discuss lipid absorption into and out of the enterocyte Into the enterocyte The products of the partial digestion of lipids cholesterol fatty acids monoacylglycerol etc and fat soluble vitamins are surrounded by bile salts micelle formation Micelles interact at the brush border of the enterocytes emptying its lipid contents into the enterocyte by diffusion down a concentration gradient This is in the duodenum jejunum The bile salts aren t absorbed until they reach the ileum Then they return to the liver via EHC portal vein enterohepatic circulation to be recycled Inside the enterocyte Fatty acids with 12 carbon atoms are activated by coupling to coenzyme A by enzyme acyl CoA synthetase Reformation fatty acids are re esterified after activation into triglycerides fatty components proteins These then leave enterocyte via chylomicrons Short chain fatty acids go from the cell into the portal blood Then they bind to albumin to be transported to liver Be able to describe the formation function and breakdown of a chylomicron Lipoproteins Function Formation Transport exogenous triglycerides and other dietary lipids to tissues other than the liver ex adipose muscle Synthesized in enterocytes from exogeneous lipids In detail Resynthesized lipids fat soluble vitamins are collected in the enterocyte s endoplasmic reticulum as large fat particles Gets lipoprotein B 48 layer on surface of particles this stabilizes particles in aqueous environment Particles pinched off as lipid vesicles then fuse to Golgi apparatus Carbohydrate attaches to protein coat then transported to cell membrane exocytosed Triglycerides are the most abundant lipid in them Breakdown Lipoprotein Lipase LPL Hydrolysis in chylomicrons happens via this enzyme Triglycerides to free fatty acids and glycerol book states diacylglycerols These are then quickly absorbed by the tissue cells Chylomicron remnants leftovers after LPL hydrolysis in chylomicrons rich in cholesterol taken up by hepatocytes Know the relationship between density size and protein for lipoproteins Higher lipid concentration lower density Lipoprotein Chylomicron VLDL IDL LDL HDL Composition Apolipoproteins A B C E 1 2 Triglycerides 80 Phospholipids cholesterol 15 Apolipoproteins B C 8 Triglycerides 50 Cholesterol 20 Phospholipids 20 brief stage between VLDL LDL where triglycerides are removed Apolipoproteins B100 21 Triglyceride 9 Cholesterol 50 Phospholipids 23 Apolipoproteins A C D E 50 Triglycerides 3 Cholesterol 20 Phospholipid 30 Size 90 100nm largest lowest density 30 90nm n a 20 25nm 5 25 nm Know the formation and function of each lipoprotein Lipoprotein Function Formation Chylomicron VLDL IDL LDL HDL Transport exogenous triglycerides and other dietary lipids to tissues other than the liver ex adipose muscle Transport endogenous lipids from liver to non hepatic tissues LPL hydrolyses it to free fatty acids glycerol forms IDL then LDL Brief stage between VLDL LDL LPL hydrolyses it to LDL Major cholesterol carrier to tissues where it ll be used for membrane construction or conversion into other metabolites like steroids Reverse cholesterol transport remove it from non hepatic tissues
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