Where are brush border enzymes located, and what is their function?

• A. On microvilli of absorptive cells in the small intestine; they digest disaccharides and other carbohydrates at the brush border
• B. On cilia of lung cells; move mucus
• C. In goblet cells; secrete mucin
• D. In basal lamina; anchor tissue

Answer: (A)

Brush border enzymes are anchored on the microvillar membrane of absorptive enterocytes in the small intestine. The microvilli create a large surface area and place these enzymes right where digestion and absorption occur, so disaccharides like lactose, sucrose, and maltose are split into monosaccharides (glucose, galactose, and fructose) at the brush border to be absorbed immediately. The other descriptions refer to structures involved in different tissues or functions—cilia in the lungs move mucus, goblet cells secrete mucin, and the basal lamina anchors tissue—so they don’t describe the location or role of brush border enzymes.