Question

Why are humans unable to digest cellulose?

• A. Because humans don't eat plants.
• B. Because humans are mostly non-vegetarians.
• C. Because of the acidic medium (HCl) in the stomach.
• D. Because humans lack appropriate enzymes to break down cellulose.

Answer 1

The correct option is D Because humans lack appropriate enzymes to break down cellulose.

Humans are unable to digest cellulose because we lack appropriate enzymes (cellulase) to break down this complex substance, cellulose. Undigestible cellulose is the fibre which aids in the smooth working of the intestinal tract. Ruminants are mammals that can break down cellulose with the help of certain microorganisms. When plant material, such as grass, enters a cow's stomach, microorganisms immediately get to work to break it down. They do this with enzymes.