1. CHEM 1152 Dr. Sheppard Spring 2015
Chapter 18: Lipids
CHEM 1152
Dr. Sheppard
Spring 2015

2. Lipids One of 4 major classes of compounds found in living tissue
Nucleic acids, proteins, carbohydrates, lipids
Specific types differ in structure
Includes fats, oils, cholesterol
Insoluble in water (large nonpolar section)
Soluble in organic solvents
Energy storage
Cell membranes
Insulation
Hormones/messengers
Some vitamins

3. 18.1 Classification of lipids
Saponifiable = esters
Simple = two components (fatty acid and alcohol)
Complex = more than two components

4. Some example lipid structures

5. 18.2 Fatty acids (FAs) Simplest type of lipid
Component of other more complex lipids
Carboxylic acid with long (10-20) carbon chain
Even number of carbons
Typically unbranched

6. Fatty acids and micelle formation

7. Saturated vs. unsaturated fatty acids
Saturated (“bad” fat)
Only C─C
Highly flexible
Pack together
Unsaturated (“good” fat)
Contains C═C
Cis double bonds
“Kink” in chain reduces possibility of heart disease
Don’t stick to walls of blood vessels
Promote blood flow
Monounsaturated
Polyunsaturated

8. Essential fatty acids Not synthesized by the body
Needed as precursors for essential molecules
Must be obtained from the diet
Plant and fish oils
Linoleic acid (18 carbons, 2 double bonds)
Linolenic acid (18 carbons, 3 double bonds)

9. Some important unsaturated fatty acids
Oleic acid (18:1)
Olives
18 carbons, C=C at C9
Linoleic (18:2)
Corn, soybean oil
Essential FA
Omega-6 FA
Linolenic acid (18:3)
Corn, fish oil
Omega-3 FA

10. Physical properties of fatty acids
Solubility
Insoluble in water
Soluble in organic solvents (ether, chloroform)
Melting point
Saturated = solid at room temperature
MP increases with longer chains
MP decreases with number of unsaturations

12. 18.3 Structure of Fats and oils
Triglycerides/triacylglycerols (TAGs)
Most abundant class of lipids in animals
Fatty acid triesters of glycerol
Formed from esterification

13. Triglycerides Function Stored in adipocytes throughout the body
Energy reserves
Insulation
Stored in adipocytes throughout the body
Hydrolyzed as needed by enzymes called lipases

14. Triglycerides Mixed vs. simple mp determined by degree of unsaturation
More unsaturation in plants than in animals
“Fat” = mostly saturated
Solid at room temperature
Meat, butter (animal sources other than fish)
“Oil” = mostly unsaturated
Liquid at room temperature
Olive oil, peanut oil (fish and plants)

15. Triglycerides

16. Mixed or simple? Fat or oil?