Lactose hydrolysis yields glucose and galactose. Based on this information, which term correctly describes lactose?

• A. Disaccharide
• B. Amino acid
• C. Nucleotide
• D. Fatty acid

Answer: (A)

Understanding what lactose is based on its hydrolysis products helps here. Lactose is a carbohydrate formed by linking two monosaccharides, glucose and galactose, with a glycosidic bond. When hydrolyzed, that bond breaks and you get glucose and galactose as separate molecules. That means lactose is a disaccharide—a sugar made of two simple sugars. The other terms describe completely different types of molecules: an amino acid is a protein building block, a nucleotide is part of nucleic acids, and a fatty acid is a component of fats. Since lactose is a carbohydrate composed of two monosaccharides, the disaccharide description fits best.