Describe the transport of glucose from the intestinal lumen into the intestinal cells and mention how Na+-K+ pumps make this process possible
What will be an ideal response?
Glucose is transported from the intestinal lumen into the intestinal cells via cotransport (secondary active transport) with Na+ ions. The symporter for this process is called SGLT (sodium-glucose transporter). A sodium ion attaches to the SGLT and increases the carrier's affinity for glucose. A glucose molecule then binds to the luminal side of the SGLT. Having a Na+ ion and glucose attached simultaneously causes the SGLT to change shape and transport the Na+ and glucose into the cell. The Na+ ion is moved down its concentration gradient, while the glucose is moved against its concentration gradient. By constantly pumping Na+ ions out of the cell, the Na+-K+ pumps in the membrane of the intestinal cell maintain a steep gradient for Na+. Therefore, Na+ ions have a greater tendency to attach to the luminal side of the SGLT, which, in turn, allows more glucose to enter the cell.
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