Monounsaturated fatty acids have how many double bonds?

• A. one double bond
• B. zero double bonds
• C. two double bonds
• D. three double bonds

Answer: (A)

Monounsaturated fatty acids have one double bond. That single carbon–carbon double bond reduces the number of hydrogens by two compared to a fully saturated chain of the same length, and it introduces a bend in the molecule. This structural feature differentiates them from saturated fatty acids, which have no double bonds, and from polyunsaturated fatty acids, which have two or more double bonds. An example is oleic acid, which has one double bond in its long hydrocarbon chain.