Cellulose belongs to carbohydrates.
Cellulose is classified as a carbohydrate, a polysaccharide, as they are formed of the glucose monomers chain. It is the prime component in the walls of the cells of plants, assisting the plants to remain upright and stiff. Humans cannot digest cellulose due to the absence of cellulase, however, it is essential in the diet as fiber.
However, the animals like sheep, cows, and horses can digest cellulose that is why they can acquire nutrients and energy they require from the grass.
