Name three digestive enzymes, their substrates, and where they act.

• A. Amylase digests starch in the mouth and small intestine; Pepsin digests proteins in the stomach; Lipase digests lipids in the small intestine.
• B. Amylase digests proteins in the stomach; Pepsin digests fats in the mouth; Lipase digests carbohydrates in the small intestine.
• C. Amylase digests lipids in the small intestine; Pepsin digests starch in the mouth; Lipase digests proteins in the stomach.
• D. Amylase digests starch in the mouth and small intestine; Pepsin digests proteins in the stomach; Lipase digests carbohydrates in the small intestine.

Answer: (A)

Digestive enzymes act on specific substrates and work in particular regions of the digestive tract. Amylase targets starch (a carbohydrate) and is active in the mouth as salivary amylase and continues in the small intestine with pancreatic amylase. Pepsin targets proteins and functions in the stomach in the acidic environment. Lipase targets lipids (fats) and works mainly in the small intestine, where pancreatic lipase digests triglycerides with the help of bile for emulsification. This combination accurately pairs each enzyme with its substrate and its site of action, making it the best choice.