Which transporter primarily mediates glucose uptake into enterocytes?

• A. GLUT4
• B. SGLT1
• C. GLUT2
• D. Na+/K+ ATPase

Answer: (B)

Glucose uptake into enterocytes is driven by a sodium-glucose co-transporter on the apical (luminal) membrane, which moves glucose into the cell together with sodium. This transporter uses the sodium gradient created by the Na+/K+ ATPase on the basolateral side. In other words, the energy for bringing glucose into the cell comes from the Na+ gradient, not from direct ATP use by a glucose transporter. Once inside, glucose can then leave to the blood via GLUT2 on the basolateral membrane. The other options don’t fit this role: GLUT4 is insulin-responsive and not present in enterocytes, GLUT2 primarily handles glucose exit to blood (and can be involved apically only under certain conditions), and Na+/K+ ATPase maintains the ion gradient rather than transporting glucose itself.