Carbohydrates are essential biomolecules that serve various functions in living organisms, including energy storage and structural integrity. They can be classified into simple carbohydrates, such as monosaccharides and disaccharides, and complex carbohydrates, including oligosaccharides and polysaccharides. One of the simplest forms of carbohydrates, the monosaccharides, is known for its role as a primary source of energy. Which of the following statements correctly describes a characteristic of monosaccharides?