Brush-border enzymes are located on the microvilli of absorptive cells in which part of the GI tract?

• A. Esophagus
• B. Stomach
• C. Small intestine
• D. Large intestine

Answer: (C)

Brush-border enzymes line the microvilli of absorptive enterocytes, giving the small intestine its ability to complete digestion right at the site of absorption. The microvilli dramatically increase surface area, and the enzymes anchored on their membranes—such as lactase, sucrase, maltase, and various peptidases—finish carbohydrate and peptide digestion just before the nutrients are taken up into the cells. The esophagus and stomach lack this dense brush-border setup, concentrating on propulsion and gastric digestion rather than final luminal digestion at the cell surface. The large intestine mainly absorbs water and electrolytes and has minimal brush-border enzymatic activity. So, these enzymes are located on the small intestine’s absorptive cells.