A wax is made up of a long-chain fatty acid and a long-chain alcohol joined by:

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11ecba2d_1293_bf55_a3bf_03c0d106d97f_MD0008_00 Lipids are hydrophobic molecules that are classified based on characteristics such as length, linkage type, and solubility. These molecules are broadly classified as hydrolyzable (lipid contains hydrolyzable ester or amide linkages) or nonhydrolyzable (lipid does not contain hydrolyzable ester or amide linkages). The hydrolyzable lipids, such as phospholipids, glycolipids, and waxes, are further classified based on the structure of their backbone (glycerophospholipids, glycosphingolipids, etc.). Waxes are an example of a hydrolyzable lipid that serves as a form of protection in plants and animals. Waxes are made up of a long-chain fatty acid and a long-chain alcohol. The wax forms when the acid and the alcohol combine through dehydration to form an ester bond. (Choice A) Amide linkages are present in sphingolipids but not in waxes. For an amide to form, the carboxyl group of the fatty acid would need to combine with an amine rather than an alcohol. (Choice C) Like esters, anhydrides are carboxylic acid derivatives. However, for an anhydride to form, the carboxyl group from the fatty acid would need to combine with an acid chloride rather than an alcohol. (Choice D) A glycosidic bond joins a sugar to another molecule. Because waxes are composed of a fatty acid and an alcohol and do not contain sugars, a glycosidic bond cannot be present. Educational objective: Lipids are hydrophobic molecules broadly classified as hydrolyzable or nonhydrolyzable, and more specifically classified based on their backbone structure. Waxes are hydrolyzable lipids that contain an ester bond formed by the linkage between a long-chain fatty acid and a long-chain alcohol.

A Wax Is Made Up of a Long-Chain Fatty Acid