AAMC FL Practice Exam

What is the structure of triacylglycerols?

1. Two fatty acids linked to a glycerol

2. Three fatty acids ester-linked to a single glycerol

3. Three glycerol molecules linked together

4. One fatty acid linked to two glycerols

The correct answer is: Three fatty acids ester-linked to a single glycerol

Triacylglycerols, also known as triglycerides, are composed of a glycerol backbone esterified to three fatty acids. The glycerol molecule, which is a three-carbon alcohol, serves as the structural foundation. Each of the three hydroxyl (-OH) groups of glycerol forms an ester bond with a fatty acid. This esterification process involves the removal of a water molecule as the fatty acid and glycerol react. The structure of triacylglycerols is significant because it determines their role in biological systems, particularly as a major form of energy storage in organisms. When fat is metabolized, it can be broken down into fatty acids and glycerol, which can then be utilized for energy production. This specific arrangement of three fatty acids linked to one glycerol differentiates triacylglycerols from other lipid structures, such as phospholipids and diglycerides, which have varying numbers and types of fatty acid chains and may include additional functional groups.