Download (fatty acid and alcohol) Complex = more than two components

Chapter 18: Lipids
CHEM 1152
Dr. Sheppard
Spring 2015
Lipids
• One of 4 major classes of compounds found in living tissue
– Nucleic acids, proteins, carbohydrates, lipids
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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
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18.1 Classification of lipids
Saponifiable = esters
Simple = two components (fatty acid and alcohol)
Complex = more than two components
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Some example lipid structures
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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
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
O
C
OH
O
OH
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Fatty acids and micelle formation
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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
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Essential fatty acids
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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)
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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
– Essential FA
– Omega-3 FA
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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
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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
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Triglycerides
• Function
– Energy reserves
– Insulation
• Stored in adipocytes
throughout the body
– Hydrolyzed as needed by
enzymes called lipases
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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)
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Triglycerides
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Mixed or simple? Fat or oil?
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