26.3. Lipids http://www.ck12.org
Waxes
Waxes are another type of lipid molecule. Waxesare esters of long-chain fatty acids and long-chain alcohols.
Waxes are soft solids with low melting points that are insoluble in water. Illustrated below (Figure26.22) is the
structure of cetyl palmitate, a natural wax present in sperm whales.
FIGURE 26.22
Cetyl palmitate belongs to the category of
compounds called waxes. It is derived
from a fatty acid that is 15 carbons in
length and an alcohol that contains 16
carbon atoms.One of the best-known natural waxes is beeswax, though many other animals and plants also synthesize waxes.
Waxes can be found on the leaves of plants and on the skin, hair, or feathers of animals, where they function to keep
these structures pliable and waterproof. Humans take advantage of the protective properties of natural and synthetic
waxes in such applications as floor polish and car wax.
Lesson Summary
- Lipids are a class of biomolecules that includes, oils, fats, and waxes. Lipids do not dissolve well in water
because of their long carbon chains. - A triglyceride is derived from the esterification of glycerol with three fatty acids.
- Phospholipids form a bilayer in which only the hydrophilic heads of the molecules are exposed to water. These
bilayers form the structure of cell membranes. - Waxes are soft, low-melting solids formed from long-chain fatty acids and alcohols.
Lesson Review Questions
Reviewing Concepts
- What physical property of lipids is distinctly different from those of other biomolecules, such as carbohydrates
and amino acids? - Describe the difference between fats and oils.
- Explain how glycerol is capable of undergoing a reaction with three fatty acid molecules in the production of
a triglyceride. - Why are fats with one or more double bonds called unsaturated?
- How do phospholipids behave in water?
- What are the roles of phospholipids and proteins in a cell membrane?
- What organic compounds combine to form a wax?