Chapter 6 Lipids Lipids aka Fats Contain C H O Reattaching a fatty acid to glycerol that has lost a fatty acid Ester bonds in process creates a water Contain much more C H than O molecule Do not readily dissolve in water Our digestive juices and blood are water based Give a creamy mouth feel adds flavor Essential fats for health Not all fats are created equally Fats solid and oils liquid Provide 9 kcals gm Lipid Family Triglycerides Fatty acids Most common type of lipid in our food and body 95 of fats we eat 95 of fat stored Phospholipids Sterols Triglycerides Structure 3 fatty acids attached to a glycerol backbone All the fatty acids can be the same or different Monoglycerides acids Diglycerides loses a fatty acid Changing the Structure of a Triglyceride Esterification Process of attaching a fatty acid to glycerol One water molecule is formed with each ester bond De esterification Removal of a fatty acid from glycerol Free fatty acid Uses a water molecule to break off Re esterification Free Fatty Acids FFAs Methyl group CH3 at one end omega end Carboxyl group COOH at the other end Alpha end FFAs differ by Number of Carbons H saturation shape of chain straight or bent Carbon Chain Length Long chain fatty acids LCFA 12 or more carbon atoms Transported via lymphatic system Fats from beef pork and lamb Medium chain fatty acids MCFA 6 to 11 carbons Transported via circulatory system Coconut and palm kernel oils Short chain fatty acids SCFA Less than 6 carbons Transported via circulatory system Fat in dairy products butter whole Saturation of Fatty Acids FAs Saturated fatty acid 0 double bonds Monounsaturated fatty acid 1 double bond Polyunsaturated fatty acid More than 2 double bonds Shape of Fatty Acids Unsaturated cis fatty acid H attached to double bond are on the same sides bent or kinked carbon chains Occur naturally Saturated trans fatty acid loses 2 fatty milk H attached to double bond are on opposite sides straight carbon chains hydrogenation creates trans polyunsaturated fats and force hydrogen to break bond to form trans moves stable and solid at room temp margarine Naming Fatty Acids Omega System Indicates where the first double bond closest to the methyl omega end occurs Delta System Uses the carboxyl end and indicates where all the double bonds occur Essential Fatty Acids EFAs PUFAs Alpha Linolenic acid An omega 3fatty acid Eicosanoids EPA and DHA fish Linolenic acid An omega 6 fatty acid Eicosanoids hormone like substance pro inflammatory Dihomo gamma linolenic acid arachidonic acid soybeans Food Sources of Triglycerides Animal fats Vegetable oils Diary products Low fat products are available Grains Naturally low in fat except when fat is added e g pastries pancakes Fruits and Vegetables Naturally low in fat except coconut and avocados Functions of Triglycerides Provide energy Main energy source for all body cells except nervous system and RBC 9 kcals gm Provide compact energy storage stable and calorie dense Nearly limitless storage Insulation Protection Subcutaneous and visceral fat Subcutaneous helps keep body at a normal temperature Visceral helps the organs from getting jostled around Aid in Fat soluble vitamin absorption transport Vitamins A D E K Essential fatty acid functions Eicosanoids have over 100 different actions Phospholipids Lipid consisting of a glycerol 2FA phosphate group Hydrophilic head Hydrophobic tail 2 main functions Component of cell membrane emulsifier Sources Synthesized Food Sterols Carbons arranged in many rings Most well known sterol is cholesterol Functions steroid hormone bile cell membranes Sources Synthesized by our bodies Foods animal products Plants are sources of other sterols Can reduce absorption of cholesterol risk of CVD Recommended Fat Intake No RDA AMDR 20 35 of total calories Saturated Trans Cholesterol as low as possible Omega 6 5 Omega 3 0 6 1 2 Mediterranean Diet Up to 40 of calories from monounsaturated Diet is rich in Olive oils fruits vegetables whole grains beans nuts and seeds Diet has small intakes of Cheese yogurt wine with meals and fish weekly intake Diet limited Red meat and eggs Regular exercise Intake has doubled in the last century Our Fat Intake Omega 6s is plentiful Omega 3s is low Food sources cold water fish walnuts flax seeds canola Supplements 650 mg EPA DHA Caution Prolonged bleeding Fat Digestion Mouth lingual lipase Stomach gastric lipase short and medium chained TGs TGs monoglycerides diglycerides FFA Small Intestine Presence of fat triggers Hormone CCK from intestinal cells CCK stimulates bile release from gallbladder lipase and collapse from pancreas Bile emulsified fat into tiny droplets called micelles Bile forms a shell micelles are acted upon by pancreatic lipase to break into monoglycerides and FFA s Colipase assists pancreatic lipase in attaching Fat Digestion in the Small Intestine TGs are broken down into monoglycerides FFA By pancreatic lipase Phospholipids are broken down into FFAs glycerol phosphoric acid other components e g choline By pancreatic phospholipase enzymes and SI enzymes cholesterol esters are broken down to cholesterol FFAs By pancreatic cholesterol esterase Fat Absorption Micelles absorbed in the duodenum and jejunum of the SI Short and medium FAs are absorbed via the portal vein then to liver then to rest of body Long chain FAs are re esterifired packaged into chylomictons enter the lymphatic system Bile is recycles via enterohepatic circulation in the ileum Transporting Fat in the Blood Fat is transported as lipoproteins Lipid core shell composed of proteins phospholipids and cholestrerol Types chylomicrons the SI to cells carries fat from VLDL made by liver to cells carries lipids take up and LDL carries cholesterol made by liver and from other sources to cells HDL helps remove cholesterol Transferring TGs into Body Cells The enzyme lipoprotein lipase sits on the surface of cells Blood vessels muscles fat adipose tissue etc LPL transfers TGs for energy use or storage muscles tend to use adipose tend to store Lipid storage in adipose LPL breaks down TG into MG and 2FA Both enter adipose cell and are reformed into TG Pathways for Cholesterol Uptake Receptor Pathway LDL take up by cell broken down and components are utilized Excess in blood becomes oxidized by free radicals Scavenger pathway WBC remove oxidized LDLs Cholesterol can build up in these cells and kill them Overtime the cholesterol filled scavengers build up on the inter blood vessel walls This results in