Most animals cannot digest cellulose.

• A. It is a protein
• B. It is digestible by all animals
• C. It is produced by plants
• D. True

Answer: (D)

Cellulose is a plant-produced carbohydrate made of glucose units linked by beta-1,4 bonds, and most animals lack the enzyme cellulase needed to break those bonds. Without cellulase, cellulose isn’t digested for energy, so it remains as dietary fiber in the gut. This is why the statement is true for the majority of animals. There are exceptions—certain herbivores and termites harbor gut microbes that produce cellulase, enabling digestion in those cases—but they are not the norm. Note that cellulose is not a protein (it’s a carbohydrate), and while plants produce it, that production fact isn’t the point when considering whether animals can digest it.