Triglycerides are composed of glycerol bonded to how many fatty acids?

• A. One fatty acid
• B. Two fatty acids
• C. Four fatty acids
• D. Three fatty acids

Answer: (D)

Triglycerides are built from a glycerol backbone that has three hydroxyl groups, and each of those hydroxyls can form an ester bond with a fatty acid. When all three are esterified, you have three fatty acids attached to glycerol, which is why this molecule is called a triglyceride—“tri” means three. This arrangement also explains why monoglycerides (one fatty acid) and diglycerides (two fatty acids) exist as distinct lipid forms, and why glycerol cannot accommodate a fourth fatty acid. The three-fatty-acid structure is key to the high energy density of triglycerides, making them ideal for long-term energy storage.