Ion transporters are \"linked\" together - not physically, but as a consequence
ID: 52805 • Letter: I
Question
Ion transporters are "linked" together - not physically, but as a consequence of their actions. For example, cells can raise their intracellular pH, when it becomes too acidic, by exchanging external Na+ for internal H+, using a Na+_H+ antiporter. The change in internal Na+ is then compensated for by using the Na+_K+ pump. Can these two transporters, operating together, normalize both the H+ and the Na+ concentrations inside the cell? Does the linked action of these two pumps cause imbalances in either the K+ concentration of the membrane potential?Explanation / Answer
A) Yes they can. As the cells become acidic, by using the Na+-H+ antiporter, excess H+ are pumped outside the cell and Na+ inside... This raises the intracellular pH. These excess Na+ are pumped outside by the Na+-K+ ATPase pumps which pump out 3Na+ for every 2K+ pumped inside the cell.
B) As more and more Na+ enter the cell through the antiporter, more and more Na+ are pumped out and more and more K+ are pumped inside the cell... This does raise the internal concentration of K+.
Excess pumping out of Na+ leads to a net decrease in positive charge inside the cell... As only 2K+ are pumped in for every 3Na+, thus there is a net decrease in membrane potential inside the cell.
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