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Nitri Sci ch. 6 - Brian Oliver Chapter 6 Lipids...

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Brian Oliver February 20, 2008 Chapter 6: Lipids Introduction 1. lipids are hydrophobic: “water-hating” or repelled by water 2. lipids are lipophilic: “fat-loving” or attracted by lipids 3. carbohydrates and protein are both water soluble, whereas lipids are not a. so carbs/protein would be hydrophilic and lipophobic 4. lipids in foods are called “fats” or “oils” 5. modern diets have too much lipid a. high fat intake contributes to cancer, heart disease, and obesity b. Americans eat too much animal fat An Ecological Perspective 1. some of the carbohydrate plants make is converted to lipid a. used for cell membrane structure b. contain very little lipid overall 2. nuts and seed oils (sesame, sunflower) are high in fat, as well as avocado and olives 3. in nature, lipid is mostly in the fat of animals a. animals contain little carbohydrate b. herbivores and carnivores alike store excess lipid as fat 4. organic compounds: complex chemicals containing carbon and hydrogen a. inorganic carbon = carbon dioxide b. carbon leaves the biosphere as animal waste, and rejoins the soil i. animal and plant remains become fossil fuel (coal/petroleum) ii. using coal/petroleum produces carbon dioxide iii. carbon dioxide is then returned to the atmosphere 5. plants retain more heat when we produce more carbon dioxide (global warming) a. climate change affects food production, animal supply, etc. Structure of Lipids 1. Fatty Acids and Triglycerides a. Triglyceride: a type of lipid formed by 3 fatty acids on a glycerol backbone i. Most of the lipid in our diet and bodies is triglyceride b. Fatty Acid: a lipid formed of long chains of Carbon atoms (4-22 atoms), which is saturated by Hydrogen to varying degrees i. Each carbon has 1-2 hydrogens attached to it except the ends ii. Omega end: ends in a 3 rd H ( methyl group ) iii. Alpha end: ends in a carboxyl group iv. Valence: each element forms a certain number of bonds with other atoms- this number is its valence 1. determines structure/properties of molecules 2. Valence values: H=1, O=2, N=3, C=4 v. No food is composed of a single fatty acid (always a mix) c. Chemical Bond: the sharing of electrons between 2 or more atoms i. More stable configuration for the electrons ii. Number of bonds predicted by valence d. Types of Fatty Acids: i. Saturated Fatty Acid : all the C-C bonds are single, saturated with Hydrogen atoms (bonded to all the hydrogen it can)
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1. the single bonds mean saturated fatty acids are very linear 2. freezes faster since it’s arrangement is more orderly 3. saturated fats are solid at room temperature 4. raise blood cholesterol a LOT (contributes to heart disease) 5. mostly animal fats a. beef, pork, chicken b. also tropical oils: palm, coconut, palm kernel ii. Monosaturated Fatty Acid: contains a single double bond in its structure 1.
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