| 1.5 Lipids |
|---|
Summary
Lipids are nonpolar, hydrophobic molecules whose diverse functions depend on how their subcomponents are assembled.
Fatty Acids
-
The building blocks of many lipids
-
Classified as saturated (straight chains with only single bonds) or unsaturated (kinked chains due to one or more double bonds)
The degree of unsaturation directly determines the physical state of a lipid: more double bonds mean more kinks, less tight packing, and a more liquid consistency at room temperature. This structure-to-property relationship is a central concept tested on the AP exam.
Different classes of lipids carry out distinct biological roles.
Fats
-
Store energy efficiently
-
Can provide insulation in mammals
Steroids
- Function as hormones regulating growth, metabolism, and homeostasis
Cholesterol
- Stabilizes animal cell membranes by moderating fluidity
Phospholipids
-
Amphipathic structure
-
Spontaneously form the lipid bilayers that make up all cell membranes
At a Glance
| Lipid Class | Biological Role | Structural Detail |
|---|---|---|
| Fats | Store energy efficiently and can provide insulation in mammals | |
| Steroids | Function as hormones regulating growth, metabolism, and homeostasis | |
| Cholesterol | Stabilizes animal cell membranes by moderating fluidity | |
| Phospholipids | Spontaneously form the lipid bilayers that make up all cell membranes | Amphipathic structure |
In every case, the biological function of a lipid traces directly back to its molecular structure — a theme that recurs throughout AP Biology.