What are the two kinds of fatty acids?

• A. saturated and trans
• B. monounsaturated and polyunsaturated
• C. saturated and unsaturated
• D. long-chain and short-chain

Answer: (C)

Two kinds of fatty acids are saturated and unsaturated. The difference lies in the carbon–carbon bonds in the hydrocarbon chain. Saturated fatty acids have no double bonds, so every carbon is fully hydrogenated, making the chain straight and typically leading to solids at room temperature. Unsaturated fatty acids have one or more double bonds, which introduce kinks in the chain and prevent tight packing, usually resulting in liquids at room temperature. Within unsaturated fats you can have monounsaturated (one double bond) or polyunsaturated (several). Trans refers to a specific geometric arrangement around a double bond that can occur in some unsaturated fats, while long-chain versus short-chain describes chain length, not saturation. Therefore, the broad two kinds are saturated and unsaturated.