Which statement correctly describes lipids?

• A. Lipids are primarily used to store genetic information.
• B. Monomer: fatty acids and glycerol; polymer: triglycerides and phospholipids; store energy and provide protection.
• C. Lipids are hydrophilic and water-soluble.
• D. Lipids are made of amino acids.

Answer: (B)

Lipids are molecules that store energy, form cell membranes, and provide protection, and their basic building blocks are glycerol and fatty acids. In these fats and oils, glycerol serves as the backbone, while fatty acids attach to it. When a lipid uses three fatty acids with one glycerol, you get triglycerides, which are especially efficient at storing energy for later use. When a lipid has a glycerol backbone, two fatty acids, and a phosphate-containing head, you get phospholipids, which are the main building blocks of cell membranes and help create a barrier that protects the cell and controls what enters or leaves. Lipids are largely nonpolar, making them hydrophobic and not soluble in water, which is why they’re so effective at energy storage and forming membranes. The statement does not describe lipids as storing genetic information—that role belongs to nucleic acids. It also isn’t accurate to say lipids are made of amino acids, since amino acids build proteins.