Although cellulose is a carbohydrate made of polymerized glucose molecules, the usual enzymes such as amylase that break down carbohydrates in your mouth and small intestine do not have any effect on cellulose. For the most part, animals do not produce the enzyme cellulase, which catalyzes cellulose hydrolysis. How then do herbivorous organisms manage to live on plant material primarily made of cellulose?

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Herbivorous animals have evolved various mechanisms to break down cellulose. One common method is to have specialized chambers in the digestive tract that harbor populations of symbiotic anaerobic bacteria that break down cellulose. These specialized chambers can be located in the foregut or the cecum. For example, ruminants such as cows, sheep, and deer have a four-chambered stomach that includes a rumen chamber where symbiotic bacteria break down cellulose. Similarly, some herbivorous mammals such as rabbits and rodents have a large cecum where cellulose is broken down by symbiotic bacteria. These bacteria produce enzymes such as cellulase that can break down cellulose into simpler sugars that are then metabolized by the animal.

Although Cellulose Is a Carbohydrate Made of Polymerized Glucose Molecules