21. The diagram below represents a sequence of events that occurs in living things. х
are digested into
Smaller molecules
which can be synthesized into
Fat
Starch
Protein
DNA
Letter X represents
Inorganic molecules
O organic molecules
O biological catalysts
O simple sugars

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.