Through which transporter is glucose absorbed in the small intestine?

• A. SGLT1 (sodium-glucose co-transporter 1) on the apical membrane
• B. GLUT2 on the apical membrane
• C. SGLT2 on the basolateral membrane
• D. GLUT4 on the basolateral membrane

Answer: (A)

Glucose entry from the intestinal lumen into the enterocytes is driven by a sodium-glucose co-transport mechanism on the apical (lumen-facing) surface. This transporter brings glucose into the cell together with Na+ by using the sodium gradient. That gradient is kept steep by the Na+/K+ ATPase on the basolateral membrane, which pumps sodium out of the cell and powers the uptake of glucose.

Once inside the cell, glucose exits into the bloodstream via a facilitated glucose transporter on the basolateral side, typically GLUT2, which moves glucose down its concentration gradient without using sodium.

Other transporters listed aren’t arranged for this uptake: SGLT2 is a kidney transporter, GLUT4 is insulin-responsive mainly in muscle and fat, and GLUT2 on the apical membrane isn’t the standard route for intestinal absorption. The apical sodium-glucose co-transporter is the key transporter for absorbing glucose from the small intestine.