Which statement best describes chemical digestion?

• A. Chemical digestion is the physical breakdown of food
• B. Involves absorption of nutrients
• C. Involves movement of food through the GI tract
• D. Involves breakdown of food with enzymes

Answer: (D)

Chemical digestion is the enzymatic breakdown of complex food molecules into smaller, absorbable units. Enzymes catalyze hydrolysis of bonds in carbohydrates, proteins, and lipids, turning starches into sugars, proteins into amino acids, and fats into fatty acids and glycerol. This process is driven by various enzymes from saliva, stomach, and the pancreas with their respective environments, enabling nutrients to become small enough for absorption. In contrast, mechanical digestion refers to the physical crushing and mixing of food, absorption is the uptake of nutrients across the intestinal lining, and movement through the GI tract is propulsion. So the statement describing chemical digestion as the breakdown of food with enzymes best captures the key idea.