What is the principal functional role of brush border enzymes in the small intestine?

• A. They complete the final steps of carbohydrate and peptide digestion at the enterocyte surface so products are small enough (monosaccharides, di/tripeptides, amino acids) for immediate absorption into epithelial cells
• B. They secrete bile and pancreatic enzymes directly into the lumen to emulsify fats before pancreatic secretions arrive
• C. They pump iron and calcium into the lumen to increase mineral concentrations and slow absorption
• D. They primarily synthesize large complex carbohydrates de novo to be exported into the bloodstream

Answer: (A)