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Chapter 13 Lipids Sections 13.1-13.3

Chapter 13 Lipids Sections 13.1-13.3. Found in living organisms They are insoluble in water but soluble in nonpolar solvents (diethyl ether) Lipids are defined by property and not structure

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Chapter 13 Lipids Sections 13.1-13.3

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  1. Chapter 13 LipidsSections 13.1-13.3

  2. Found in living organisms • They are insoluble in water but soluble in nonpolar solvents (diethyl ether) • Lipids are defined by property and not structure • Stores energy in fat cells, part of membranes that separate aqueous solutions, and serve as chemical messengers 13.1 What are Lipids?

  3. Fat energy burn about 9kcal/g and carbohydrates are only 4kcal/g • Lipids provide membranes for the body and has hydrophobic properties • Steroid hormones deliver signals from one part to another • We can classify lipids into four groups • Simple lipids, such as fats and waxes • Complex lipids • Steroids • Prostaglandins, thromboxanes, and leukotriens

  4. Animal fats and plant oils are triglycerides • Triglycerides are triesters of glycerol and long-chain carboxylic acids called fatty acids • Triglycerides are always glycerol • Practically all unbranched carboxylic acids • Even number of carbons; 10-20 • No other functional group besides –COOH and double bonds 13.2 What Are the Structures of Triglycerides?

  5. The cis isomers predominate • There are mono- and diglycerides but are less common

  6. Fats from animals are usually solid but fats from plants or fish are liquid • Liquid fats are called oils • Solid animal fats contain mostly saturated fatty acids • Vegetable oil contains high amounts of unsaturated fatty acids 13.3 What Are Some Properties of Triglycerides?

  7. Linoleic and linolenic acids are called essential fatty acids; the body cant synthesize them so they need to be consumed • Most vegetable oil has high amounts of unsaturated fatty acids • Exception: coconut oil • Oils with more than one double bond per fatty acid chain are called polyunsaturated • Pure fats and oils are colorless, odorless and tasteless • Tastes, odors and colors are caused by small amounts of other substances dissolved in the fat or oil

  8. Unsaturated liquid oils are converted to solids • Carbon to carbon double bonds are reduced to single bonds by treating them with hydrogen and a catalyst • Fats with no double bonds would be too solid Hydrogenation

  9. Source of trans fatty acids • Partial hydrogenation creates a product with the right consistency for cooking • Produces Crisco, Spry and Dexo • Margarine is made by partial hydrogenation of vegetable oils

  10. Oldest known chemical reaction • Glycerides are subject to hydrolysis which can be carried out with acids or bases • Base promoted hydrolysis of fats and oils producing glycerol and a mixture of fatty acid salts • Produces soaps Saponification

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