Which lipid is liquid at room temperature?

• A. Saturated fat
• B. Oil
• C. Cholesterol
• D. Wax

Answer: (B)

The liquid state at room temperature comes from having unsaturated fatty acids in the lipid. The double bonds create kinks that stop the fatty acid chains from packing tightly, lowering the melting point so the lipid remains a liquid around typical room temperatures. Oils are rich in these unsaturated fats, so they stay fluid.

Saturated fats have straight chains that pack closely together, raising the melting point so they are solid at room temperature. Cholesterol is a sterol with a rigid, complex structure, not a simple liquid lipid, and is not typically a meltable liquid at room temperature. Waxes have very long chains and strong intermolecular forces, giving them high melting points and solid form at room temperature.