Questions to Ponder Exam 2 1 What are the functions of lipids in our bodies and in foods natures way of condensing energy stores also insulates protects organs source of calories 9 kcal gram flavor and tenderness of food slows stomach emptying more satiating source of essential fatty acids 2 What are the three main types of lipids triglycerides we eat in the diet main form of fat in food made up of glycerol backbone and three fatty acids fatty acids classified by length and location of double bonds organization of hydrogen around the double bonds phospholipids glycerol two fatty acids phosphorus phosphorus part makes it soluble in water fatty acids make it soluble in fat therefore can serve as an emulsifier key role is in cell membranes sterols large molecules consisting of interconnected rings of carbon atoms with side chains of carbon hydrogen and oxygen cholesterol is found in all animal cell membranes is nonessential forms plaques that cause atherosclerosis cholesterol serves as the raw material for bile vitamin D steroid hormones including the sex hormones we need t in our body but we call it nonessential because we don t need it from diet our body makes it How are lipids digested absorbed in the body How are they transported from the 3 gastrointestinal tract to the liver What happens to them in the liver DIGESTION AND ABSORPTION is this of lipids Digestion depends on pre duodenal lipase gastric formed in mouth in infants and stomach for adults pancreatic lipase bile acids for emulsification lipase breaks down triglycerides into free fatty acids and monoglycerides Absorption short chain fatty acids portal vein blood to liver monoglycerides and longer fatty acids get repackaged as triglycerides for transport in lipoproteins chylomicrons enter lymph and then blood stream Process In the stomach the fat and watery digestive juices tend to separate Enzymes are in the water and can t get at the fat When fat enters the small intestine the gallbladder secretes bile Bile has an affinity for both fat and water so it can bring the fat into the water After emulsification more fat is exposed to the enzymes and fat digestion proceeds efficiently Transport as Lipoproteins Chylomicrons from intestines to body others produced in liver VLDLs Very Low Density Lipoproteins LDLs Low Density Lipoproteins Both take TG and cholesterol to body HDLs High Density Lipoproteins good guys scavengers of cholesterol brings it back to liver Lipid Digestion depends on pre duodenal lipase gastri pancreatic lipase bile acids for emulsification Lipase breaks down triglycerides into free fatty acids and monoglycerides Absorption Short Chain Fatty Acids portal vein blood to liver Monoglycerides and longer fatty acids gets repackaged as triglycerides for transport in lipoproteins Chlomicrons enter lymph and then blood stream Chylomicrons transport lipoproteins from intestine to body others produced in liver VLDLs LDLs both take TG and cholesterol to body HDLs scavengers of cholesterol brings it back to liver First the digestive system mixes fats with bile containing digestive juices to emulsify the fats then fat digesting enzymes can break the fats down Many fats travel from place to place in lipoproteins Inside the cells of the small intestine they form chylomicrons to safely travel in the watery bood Glycerol and short chain fatty acids travel in the bloodstream unassisted Other lipids are incorporated into chylomicrons for transport in the lymph and blood Fats need special transport vehicles the lipoproteins to carry them in watery body fluids 4 What are the differences between saturated and unsaturated fatty acids in terms of chemical structure where they are found in our diet and their impact upon human health Saturated Fatty Acids Chemical Structure a fatty acid carrying the maximum of hydrogen atoms solid Where they are found in our diet animal products Their impact upon human health heart disease Unsaturated Fatty Acids Chemical Structure a fatty acid with less than maximum hydrogen atoms monounsaturated 1 double bond and polyunsaturated more than one double bond liquid Where they are found in our diet polyunsaturated vegetable and fish oils saturated animal fats monounsaturated some vegetable oils olive oil and canola oil Their impact upon human health When polyunsaturated fat replaces saturated and trans fat in the cite the heart and blood lipids benefit Olive oil rich in monounsaturated fatty acids and antioxidant phytochemicals also benefits the heart when it replaces butter and other saturated fats in the diet It is recommended that both women and men consume unsaturated fats instead of saturated fats for heart health 5 What is trans fat Where is trans fat found in the human diet Why are we advised to eat minimal trans fat fatty acids with unusual shapes arise when polyunsaturated oils are hydrogenated advantage control consistency and oxidation of fats disadvantage increase LDL found in margarines shortenings baked goods we are advised to eat minimal trans fat because they are bad We don t need any in diet 6 What are the two essential fatty acids Where are they found in our diet Why is it important to have the proper balance of these two fatty acids in the diet the two essential fatty acids are omega 3 and omega 6 they are made in limited amounts in the body abundant in fish oils lower blood pressure prevent blood clot formation protect against irregular heartbeats may reduce inflammation essential for normal infant growth and development may support immune system may inhibit cancers we need them from our diet we don t produce them Omega 3 polyunsaturated linolenic acid docosahexaenoic acid DHA fish eicosapentaenoic acid EPA fish precursors of omega 3 eicosanoids sources of omega 3 fatty fish salmon tuna herring flaxseed canola and soybean oils almonds walnuts spinach mustard greens Omega 6 Linoleic acid we get it in our diet precursors of omega 6 eicosanoids our ratio is off we get way too many 6 and not enough 3 source of omega 6 grains fats and oils Eicosanoids hormone like compounds that are made from EFAs and act through receptors on tissues to regulate many body responses omega 6 cause inflammation blood clotting and tumor growth omega 3 reduce inflammation blood clotting and tumor growth It is important to have the proper balance because similar enzymes required for processing too much of one interferes with the other American diet too low in omega 3 average U S intake of EPA and DHA is 150
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