Waxes and carotenoids are lipid _______.

• A. derivatives
• B. esters
• C. polymers
• D. amphipathic molecules

Answer: (A)

The idea being tested is that waxes and carotenoids are lipid derivatives. Waxes are formed from fatty acids linked to long-chain alcohols, making them lipid esters tied to the fatty acid building blocks of many lipids. Carotenoids, while not esters, are built from isoprene units through terpene biosynthesis, a pathway closely connected to lipid metabolism, which gives them their strongly lipid-like, nonpolar character. Describing them as lipid derivatives highlights their origin in lipid biosynthesis and their lipophilic nature, rather than calling them simple, common fats or other unrelated classes. They are not polymers or amphipathic molecules, and carotenoids aren’t formed as esters like waxes, so “lipid derivatives” best captures their relationship to lipids.