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 acids2. 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.3. How are lipids digested/absorbed in the body? How are they transported from thegastrointestinal 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 lipasebile acids for emulsification- lipase breaks down triglycerides into free fatty acids and monoglyceridesAbsorption- 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 streamProcess- 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 efficientlyTransport 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 transfat 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 toeat 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 diet6. What are the two essential fatty acids? Where are they found in our diet? Why is itimportant 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
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