Biology · MICROBES IN HUMAN WELFARE

What is the primary reason why human beings are unable to digest cellulose present in plant foods, while cattle can efficiently utilize it?

1. Plant cell walls in cattle fodder lack lignin polymers entirely, making them completely soluble in neutral saliva.
2. Cattle possess specialized acidic gastric chambers that chemically hydrolyze crystalline cellulose into glucose monomers.
3. Human intestinal epithelial walls actively absorb cellulose without breakdown, leading to toxic metabolic byproducts.
4. Humans lack the enzyme cellulase as well as symbiotic cellulose-digesting bacteria in their digestive tract, whereas cattle possess methanogens in their rumen.