Exchange Surfaces Practice Test 2026 - Free Practice Questions for Exam Preparation

The correct answer is A, which refers to chemical digestion. This process involves the breakdown of food through enzymatic action, where various enzymes catalyze the hydrolysis of complex macromolecules into their simpler forms, such as carbohydrates into sugars, proteins into amino acids, and lipids into fatty acids and glycerol.

Enzymes are specific catalysts that speed up chemical reactions, allowing for the efficient breakdown of food components in the gastrointestinal tract. This process is crucial for nutrient absorption in the body, as the body can only absorb smaller, simpler molecules.

Mechanical digestion, in contrast, involves the physical breakdown of food into smaller pieces through actions such as chewing and churning in the stomach. Absorption refers to the process where the products of digestion are taken up by the cells lining the intestine and entered into the bloodstream. Fermentation is a process typically associated with the breakdown of organic substrates by microorganisms into simpler compounds, often seen in certain digestive processes, but it does not primarily involve enzymatic action in the same manner as chemical digestion does.