1. Chapter 13 Lipids Sections 13.1-13.3

2. 13.1 What are Lipids? 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

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

5. 13.2 What Are the Structures of Triglycerides?
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

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

7. 13.3 What Are Some Properties of Triglycerides?
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

9. Most vegetable oil has high amounts of unsaturated fatty acids
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

10. Hydrogenation 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

11. 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

12. Saponification 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