Fill in the blank below: in a digestive system, digestion takes place outside of the cells in a series of tubes. food enters one opening and food remnants exit out of a different opening. examples of organisms with this type of digestive system include you, dogs, horses, spiders and earthworms.

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.