What is cotransport? Explain how understanding it is used in our treatment of diarrhea.

In cotransport, a single ATP-powered pump that transports a specific solute drives the active transport of several other solutes. Normally, sodium in waste is reabsorbed in the colon, maintaining constant levels in the body, but diarrhea expels waste so rapidly that re-absorption is not possible, and sodium levels fall precipitously. To treat this life threatening condition, patients are given a solution to drink containing high concentrations of salt and glucose. The solutes are taken up by sodium-glucose cotransporters on the surface of intestinal cells and passed through the cells into the blood. This simple treatment has lowered infant mortality worldwide.