Chapter 6. LipidsLipids (aka Fats)• Contain C, H, O– Contain much more C & H than O• Do not readily dissolve in water– Our digestive juices and blood are ________________ based• Give a creamy mouth feel & adds flavor• Essential fats for health– Not all fats are created equally• Fats (lipids solid at room temp) and oils (lipids liquid at room temp)• Provide 9 kcals/gmLipid Family• Triglycerides– Fatty acids– Most common type of lipid in our food and body• 95% of fats we eat & 95% of fat stored• Monoglyceride• DiglycerideTriglycerides• Structure– 3 fatty acids attached to a glycerol backbone– All the fatty acids can be the same, or different• Monoglycerides : loses 2 fatty acids• Diglycerides : loses a fatty acidChanging 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– Reattaching a fatty acid to glycerol that has lost a fatty acid • Ester bondsFree Fatty Acids (FFAs)• Methyl group (CH3) at one end– ________________ end• Carboxyl group (COOH) at the other end– ____________________end• FFAs differ by– Number of Carbons– H saturation– shape of chain• straight or bentCarbon 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 10 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 milkSaturation of Fatty Acids (FAs)• Saturated fatty acid– 0 double bonds• Monounsaturated fatty acid– 1 double bond• Polyunsaturated fatty acid– More than 2 double bondsShape of Fatty Acids• Unsaturated cis fatty acid– H attached to double bond are on the same sides– ____________________ or ____________________ carbon chains– Occur naturally• Saturated & trans fatty acid– H attached to double bond are on opposite sides– ____________________ carbon chains– ________________________________________ creates form• What is that?Naming Fatty Acids• Omega System– Indicates where the first double bond closest to the methyl end occurs• Delta System– Uses the carboxyl end and indicates where all the double bonds occurEssential Fatty Acids (EFAs) (PUFAs)• Linolenic acid– An omega-6 fatty acid– Eicosanoids• Regulates BP and increases clotting• Alpha-linolenic acid– An omega-3 fatty acid– Eicosanoids • Dihomo-gamma-linolenic acid arachidonic acidFood 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 coconutand avocadosFunctions 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 actionsPhospholipids• Lipid consisting of a head + tail + phosphate group• Hydrophilic head & Hydrophobic tail• 2 main functions– Component of cell membrane– emulsifier• Sources– Synthesized– FoodSterols• Carbons arranged in many rings• Most well-known sterol is cholesterol• Functions : make testosterone and estrogen, vitamin D, bile• Sources – Synthesized by our bodies– Foods• Plants are sources of other sterols– Can reduce absorption of cholesterol and bile & risk of CVDRecommended Fat Intake• No RDA• AMDR: 20-35% of total caloriesSaturated, Trans, Cholesterol: as low as possibleOmega-6: 5%Omega-3: 0.6-1.2%Mediterranean Diet• Up to 40% of calories from fat• 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 Our Fat Intake• Intake has doubled in the last century• 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– __________________ lipase• __________________ and __________________-chained TGs• Stomach– __________________ lipase• TGs à • Small Intestine– Presence of fat triggers• Hormone __________________from intestinal cells• Hormone stimulates __________________ release from gallbladder & __________________ and __________________from pancreas – Bile emulsified fat into tiny droplets, called __________________– Bile forms a shell – __________________ areacted upon by pancreatic lipase to break into __________________ and __________________» Colipase assists pancreatic lipase in attachingFat Digestion in the Small Intestine • TGs are broken down into __________________ & __________________– By pancreatic __________________• __________________ are broken down into FFAs, glycerol, phosphoric acid & other components (e.g., choline)– By pancreatic __________________ enzymes andSI enzymes • __________________ esters are broken down to __________________ & __________________– By pancreatic __________________ __________________Fat Absorption • Micelles absorbed in the __________________ and __________________ of the SI– ____________________________________FAs are absorbed via the portal vein (which leads to? Then?)– ____________________________________FAs are __________________, packagedinto __________________, & enter the lymphatic system• Bile is recycles via enterohepatic circulation in the__________________Figure: Absorption of TGsFigure: Overview of Lipid Digestion andAbsorptionTransporting Fat in the Blood• Fat is transported as ____________________________________– What is it made up of?•