Chapter 6- Lipids - Chapter 6 Lipids Introduction...

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Chapter 6- Lipids Introduction Hydrophobic o “water-hating” o Repelled by water Lipophilic o “fat-loving” o attracted by lipid Lipids in foods are referred to as fats and oils o Fats are solid at room temperature o Oils are liquid Ecological Perspective Carbon is present in lipids, carbohydrate and protein o Element of life Organic compounds o A complex chemical containing carbon in its structure. o Contain carbon and hydrogen Inorganic carbon o Form of carbon dioxide in the atmosphere Photosynthesis brings carbon from the atmosphere and incorporates it into an organic form, glucose, available to life Structure 3 kinds of lipids live in the world: triglycerides, phospholipids, and sterols Fatty Acids and Triglycerides o A type of lipid formed by 3 fatty acids arrayed on a glycerol backbone. Most fats occur in the triglyceride form o Make up most of the lipid in our diet and bodies o Methyl group -CH3 o Carboxyl group -COOH o Valence The characteristic number of chemical bonds formed by a particular chemical element Determines the structure and properties of the molecules the element finds itself involved in Valence of hydrogen is 1- always forms one chemical bond Valence of carbon is 2- always forms two chemical bonds of some sort o Saturated Fatty Acids
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A fatty acid in which all of the carbon-carbon bonds are single bonds. It is saturated with hydrogen atoms, that is, it contains all the hydrogen it can in its structure. Found in animal products Carbons atoms in a saturated fatty acid fulfill the valence of 4 by each bonding with 2 other carbons and 2 hydrogen atoms Cell membranes are made up of fatty acids Having a lot of fatty acids in the membrane makes the membrane less effective at removing cholesterol from the blood o Monounsaturated Fatty Acids A fatty acid containing a single point of unsaturation, that is, a single double bond, in its structure. Found in vegetable fats Point of unsaturation A double bond in a fatty acid. Not saturated by hydrogen atoms; more hydrogen could be added were the double bond to be split Lower freezing point than saturated fats Less linear than a saturated fat Example: Olive oil, canola oil, and sesame oil Lower blood levels of cholesterol and are not associated with an increased risk of disease o Polyunsaturated Fatty Acids Fatty acid containing more than one point of unsaturation, that is, more than one double bond, in its structure. Found in vegetable fats So many double bonds mean that polyunsaturates remain fluid at low temperatures (most stay liquid in the freezer) Omega-6 Polyunsaturates Most common vegetable oils Contain linoleic acid o 18:2 Corn, safflower, soybean, cottonseed, and sunflower Lower both the desirable and undesirable types of cholesterol in the blood Omega-3 Polyunsaturates Fish oils Eicosapentanoic acid o A 20:5 omega-3 fatty acid found in fish
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Chapter 6- Lipids - Chapter 6 Lipids Introduction...

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