Question

Ruminant animals can digest cellulose in their food, where as human beings are unable to do so. This is because

• A. Methanogens are present in human gut.
• B. Cellulose is a complex sugar.
• C. Cellulose reduces the bulk of food.
• D. Methanogens are absent in human gut.

Answer 1

The Correct Option is D

Ruminants (e.g., cows, sheep) can digest cellulose because their gut hosts symbiotic microbes (bacteria, protozoa, and methanogens) that produce cellulase enzymes to break down cellulose into glucose. Humans lack these microbes (including methanogens) and thus cannot produce cellulase, making cellulose indigestible (fiber passes through the digestive system). 

Methanogens help ferment cellulose-derived compounds into volatile fatty acids (energy source) and methane (a byproduct). Their absence in humans is the primary reason for inability to digest cellulose.

Thus, the correct option is D: Methanogens are absent in human gut.