What substance is transported in intestinal epithelial cells by a Na+ dependent cotransport process?

The substance that is transported in intestinal epithelial cells by a Na+ dependent cotransport process is glucose. In the intestinal mucosa, glucose is absorbed through a mechanism that relies on the sodium gradient established by the Na+/K+ ATPase pump. This pump actively transports sodium ions out of the epithelial cells and keeps the intracellular sodium concentration low.

As sodium ions flow back into the cells through specific transporters, they drive the secondary active transport of glucose against its concentration gradient. This is facilitated by the sodium-glucose cotransporter (SGLT), allowing glucose to be absorbed efficiently from the intestinal lumen into the cells.

While alanine and other amino acids may also utilize sodium-dependent transport mechanisms, the primary and well-characterized example in the context of intestinal absorption is glucose. Fructose, on the other hand, is absorbed through a different mechanism, specifically facilitated diffusion via the GLUT5 transporter, which does not involve sodium cotransport. Thus, glucose is the most classic example of a substance that utilizes a Na+ dependent cotransport process in the intestinal epithelial cells.