Final answer:
Digestion breaks down macromolecules into smaller molecules necessary for cell absorption, with enzymes like amylase and lipase facilitating the process.
Step-by-step explanation:
Macromolecules must be broken down into smaller molecules during digestion because our body's cells can only absorb these simpler, smaller units. Enzymes play a crucial role in the chemical digestion process by catalyzing hydrolysis reactions, which break down macromolecules into their monomeric components. For example, enzymes such as amylase and lipase specialize in the breakdown of carbohydrates and lipids respectively, allowing nutrients to be efficiently absorbed in the small intestine and used by the body.