• Fats, oils, waxes
• No polymers
• Hydrophobic
– Some polar bonds
– Mostly hydrocarbons (nonpolar) so
soluble in organic solvents (gasoline)
– Smaller than true macromolecules
Subunits of Lipids
1)
Fatty Acids
• Long carbon skeleton
• Nonpolar
• Hydrophobic
• At one end, carboxyl group (thus fatty acid)
• Functions
– Energy storage
» Fats store twice as much energy as
polysaccharides
– Cushions vital organs
– Insulation
• Saturated Fatty Acids
– No double bonds between carbons
– Saturated with hydrogen
– Solid at room temperature
– All are animal fats (lard, butter) except palm
& coconut oil
– Too many = atherosclerosis
• Unsaturated Fatty Acids
– One or more double bonds
– Double bonds formed from the removal of hydrogen
– Liquid at room temp.
– Kink in H - C chain (tail) where double bonds located
– Kinks prevent molecules from packing close enough
to solidify at room temperature
– Polyunsaturated = more than one double bond
– Hydrogenated vegetable oils
» Unsaturated converted to saturated by adding H
» H prevents lipids from separating out in liquid
form
» Ex: Peanut butter, margarine
2. Glycerol
•
•
•
Backbone of fat molecule
An alcohol with 3 carbons
Each carbon has a hydroxyl group
Families
1) Fats / Triglycerides
–
–
–
–
Large molecules
Dehydration synthesis
One glycerol and 3 fatty acids (need not be identical)
Assembled through ester linkage (bond between hydroxyl
and carboxyl groups)
–
Resulting fat = triacylglycerol (triglyceride)
Dehydration Synthesis
2.
Phospholipids (Modified Fats)
–
Similar to fats, but two fatty acid tails
–
One fatty acid replace by phosphate group
(negative charge)
–
Other small molecules (polar) can be added to
form a variety of phospholipids
–
Tails are hydrophobic
–
Heads (glycerol) are hydrophilic
–
Result: When put in water, heads out and tails
in
2) Phospholipids (continued)
– In cells
•
•
•
•
Form bi-layer at surface
Heads outside and tails inside
Forms boundary between cell and external
environment
Major component of cell membrane
Hydrophilic Head
Hydrophobic Tails
Hydrophilic Head
3) Steroids
–
–
–
C skeleton with four fused rings
Different functional groups attached
Example: Cholesterol
• Anchors some phospholipids in animal cell
membranes
• Precursor from which other steroid
synthesized
– Ex: Sex hormones
• If too much → atherosclerosis