Fatty acids that are not completely saturated with hydrogens and contain one or more carbon–carbon double bonds are called what?

• A. Saturated fats
• B. Trans fats
• C. Unsaturated fatty acids
• D. Polyunsaturated fatty acids

Answer: (C)

The concept being tested is how hydrogen saturation relates to double bonds in fatty acids. When a fatty acid has no carbon–carbon double bonds, it is fully saturated with hydrogen. If there is one or more double bonds, the chain is not fully hydrogenated, which makes it unsaturated. The description “not completely saturated with hydrogens and contain one or more carbon–carbon double bonds” fits unsaturated fatty acids. If there is only one double bond, it’s monounsaturated; with multiple double bonds, it’s polyunsaturated. Saturated fats have no double bonds at all, and polyunsaturated fats are a subset of unsaturated fats with several double bonds.