Final answer:
Humans cannot digest cellulose due to the absence of the enzyme cellulase, making it pass through the digestive system as indigestible fiber. Cellulose contributes to dietary bulk and helps with gastrointestinal movement, but does not provide energy to humans as it does for certain herbivores and microorganisms that possess cellulase.
Step-by-step explanation:
Understanding the Indigestibility of Cellulose in Humans
Cellulose is a complex carbohydrate that forms the cell wall of plants and provides structural support. While herbivores can digest cellulose due to the presence of microorganisms in their digestive system that produce cellulase, humans lack the enzymes needed to break down the β-glycosidic linkages in cellulose. As a result, cellulose remains indigestible and passes through the human digestive system as fiber, adding bulk to the diet and aiding in gastrointestinal mobility.
Although cellulose is not metabolized for energy in humans, it plays a crucial role in maintaining healthy bowel movements and preventing constipation. The lack of enzymes such as cellulase in the human digestive tract means that cellulose, when ingested, acts as dietary fiber, contributing to overall digestive health without providing caloric energy.
The organic molecules required for building cellular material and providing energy, such as glucose, are derived from digestible carbohydrates, unlike cellulose. However, dietary fiber is still an essential component of a balanced diet due to its beneficial effects on the digestive system. It's important to note that despite holding energy in the form of glucose monomers within its structure, the bonds of cellulose cannot be harnessed by the human digestive system.