Which of the following options is NOT a monosaccharide?

Maltose is not a monosaccharide; it is a disaccharide. A disaccharide is formed when two monosaccharides are joined together through a glycosidic bond. In the case of maltose, it is composed of two glucose molecules linked together.

On the other hand, glucose, fructose, and galactose are all monosaccharides, which are the simplest forms of carbohydrates. Monosaccharides cannot be hydrolyzed into simpler sugars, as they already consist of a single sugar unit. This classification is important in nutrition because monosaccharides serve as the basic building blocks for carbohydrates, while disaccharides and polysaccharides (which consist of multiple sugar units) require further breakdown during digestion. Understanding these different forms of carbohydrates enhances comprehension of how they are metabolized in the body and their roles in nutrition.