AP Biology / Unit 1: Chemistry of Life
1.5 Lipids
Notes
Lipids are nonpolar (hydrophobic) and not true polymers.
- Saturated fats: no C=C double bonds, solid at room temperature.
- Unsaturated fats: double bonds cause kinks, liquid.
- Phospholipids: hydrophilic head and hydrophobic tails; form bilayers.
- Steroids: four fused rings (cholesterol, hormones).
Practice
In a phospholipid bilayer, the tails face:
Hydrophobic tails avoid water.
Olive oil is liquid at room temperature because it has:
Kinks keep molecules from packing tightly.
Lipids are hydrophobic because they are mostly:
Nonpolar molecules don't mix with water.
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