Which statement correctly identifies carbohydrates?

Which statement correctly identifies carbohydrates?

• A. They include only sugars.
• B. They include only starch.
• C. They include only cellulose.
• D. Sugars, starch, and cellulose are examples of carbohydrates.

Answer: (D)

Carbohydrates are a broad class of biomolecules that include everything from simple sugars to large polysaccharides. They are built from carbon, hydrogen, and oxygen and often have the formula (CH2O)n. The statement that sugars, starch, and cellulose are examples fits this definition because each represents a type of carbohydrate: sugars are the small, quick-energy forms (monosaccharides or disaccharides), starch is a plant storage polysaccharide, and cellulose is a plant structural polysaccharide. The key difference among them lies in structure and function, not in category: starch has alpha-linked glucose units and is digestible by many animals for energy, while cellulose has beta-linked glucose units, giving it rigidity and making it largely indigestible for humans without specific enzymes. The other options imply carbohydrates are limited to a single form, which isn’t true since the category spans simple sugars to complex polymers with varied roles.

Carbohydrates are a broad class of biomolecules that include everything from simple sugars to large polysaccharides. They are built from carbon, hydrogen, and oxygen and often have the formula (CH2O)n. The statement that sugars, starch, and cellulose are examples fits this definition because each represents a type of carbohydrate: sugars are the small, quick-energy forms (monosaccharides or disaccharides), starch is a plant storage polysaccharide, and cellulose is a plant structural polysaccharide. The key difference among them lies in structure and function, not in category: starch has alpha-linked glucose units and is digestible by many animals for energy, while cellulose has beta-linked glucose units, giving it rigidity and making it largely indigestible for humans without specific enzymes. The other options imply carbohydrates are limited to a single form, which isn’t true since the category spans simple sugars to complex polymers with varied roles.