Question

Humans cannot digest cellulose whereas cows can do so because

• A. Their gut contains certain bacteria capable of digesting cellulose.
• B. They have a many-chambered stomach.
• C. They have efficient grinding molars.
• D. They produce an enzyme cellulase which can digest cellulose.

Answer 1

The correct option is A Their gut contains certain bacteria capable of digesting cellulose.

Humans lack the enzyme necessary to digest cellulose. Hay and grasses are particularly abundant in cellulose, and both are indigestible by humans (although humans can digest starch). Animals such as termites and herbivores such as cows, koalas and horses all digest cellulose, but even these animals do not themselves have an enzyme that digests this material. Instead, these animals harbour microbes that can digest cellulose. Animals such as cows have anaerobic bacteria in their digestive tracts which digest cellulose. Cows are ruminants. Ruminants have several stomachs that break down plant materials with the help of enzymes and bacteria. The partially digested material is then regurgitated into the mouth, which is then chewed to break the material down even further. The bacterial digestion of cellulose by bacteria in the stomachs of ruminants is anaerobic, meaning that the process does not use oxygen.