Glucose absorption in the intestine involves co-transport with which ion?

• A. Sodium
• B. Potassium
• C. Calcium
• D. Magnesium

Answer: (A)

Glucose absorption in the small intestine relies on a sodium-dependent co-transport mechanism. At the brush border of enterocytes, glucose is taken up from the lumen together with sodium by a specific transporter. The driving force is the sodium electrochemical gradient, which is kept low inside the cell by the Na+/K+-ATPase pump on the basolateral membrane. This gradient provides the energy to move glucose against its own concentration gradient. After entering the cell, glucose exits into the bloodstream through a facilitated diffusion transporter on the basolateral side.

Other ions don’t participate in this glucose uptake step. Potassium helps maintain resting membrane potential but isn’t coupled with glucose transport. Calcium and magnesium are absorbed via separate, independent pathways and channels that do not involve co-transport with glucose.