Why is cellulose not a source of nutrients for humans? Humans cannot absorb the hydrolyzed form of cellulose. Humans, and most vertebrates, lack the enzyme cellulase. Cellulose is a structural carbohydrate, and therefore is not useful as an energy source. Vertebrate enzymes hydrolyze (α 1-4) glucose linkages, but not glucose in the β configuration. Cellulose digestion must occur in a basic environment, but the human gut is acidic.

"Humans" and most "vertebrates", lack the enzyme cellulose and "Vertebrate enzymes hydrolyze (a 1-4) glucose" linkages, but not glucose in the "ß configuration" these are the reasons is why cellulose is not the origin of nutrients for human beings.

Option: B and D

Explanation:

Cellulose is an example of polysaccharides (carbohydrate polymer linked with multiple glucose monosaccharide units). It is found in plants and breakdown of cellulose can only occur mainly in cows, buffaloes, horses, sheep, goats, termites etc as they have symbiotic bacteria in their intestinal tract which carry cellulose enzyme and responsible for cellulose hydrolysis in the gastro-intestinal tract. But animals cannot digest it 100% or directly. Cellulose is having glucose linked with beta acetal linkage which makes it alters from starch having alpha acetal linkage. Hence this mark reason behind the difference in digestibility of cellulose in animals and vertebrates.

The correct answer is vertebrate enzyme hydrolyze alpha-1,4 glycosidic linkage but not glucose in the beta configuration.

Explanation:

The amylase that is present inside human body is called salivary alpha amylase, an enzyme that digest the alpha-1,4-glycosidic linkages of starch but does not act on those glycosidic linkages which are present in beta configuration.

Cellulose contain beta-1,4-glycosidic linkages. That"s why it is not digested by the alpha amylase enzyme present inside the human body basically present in the saliva.