Final answer:
Cellulose in tube 6 was hydrolyzed to glucose by bacteria that produce cellulase, an enzyme that catalyzes the breakdown of cellulose into glucose monomers.
Step-by-step explanation:
The reason that cellulose in tube 6 (bacteria, cellulose, pH 7.0 buffer) was hydrolyzed to glucose is due to the presence of bacteria that produce the enzyme cellulase. Cellulase is capable of catalyzing the hydrolysis of cellulose into glucose monomers. In the case of herbivores and certain insects like termites, these microorganisms live symbiotically in their digestive systems, allowing them to utilize cellulose from plants as an energy source.
While humans and other non-herbivorous animals cannot digest cellulose because they lack the necessary enzyme, cellulase-producing microorganisms can. These enzymes break the β-glycosidic linkages in cellulose, hence transforming this polysaccharide into glucose, which can then be used for energy.