[NewtoAtoms]

Hello Chemists,

Q: Assume that the plasma membrane of a cell was suddenly permeable to the same degree to both Na+ and K+ and that teach responded to a concentration gradient of the same magnitude. Would you expect those two ions to move across the membrane at the same rates? Why or why not?

I always take a galliant effort to try to answer my own questions before posting. I have researched this possibility and come up with a solution. I am wondering you chemists would be so kind to read it and offer any additional thoughts.

A: I know that inorder for Na+ and K+ ions to move in and out of a cell they need an NA+/K+ ATase, therefore if a membrane was suddenly permeable to the same degree to both Na+ and K+ the two ions could not move across the membane at the same rate! In the second step of Na+/K+ ATPase 3 Na+ ions move out of the cell into the extracellular space reducing an ATP molecule to ADP. In turn, in the 4th step of the NA+/K+ ATPase, two K+ ions move into the cell, while also loosing an attached phosphate molecule. Therefore regardless of the sudden permeabilty change, the ration of Na+/K+ is still 3:2.

Is there something else, that I am not getting?

Thank you for your time

Newtoatoms

[UG]

All I know is that 3 Na⁺ are pumped out of the cell for every 2 K⁺ pumped in  .

[JGK]

Q: Assume that the plasma membrane of a cell was suddenly permeable to the same degree to both Na+ and K+ and that teach? (each) responded to a concentration gradient of the same magnitude. Would you expect those two ions to move across the membrane at the same rates? Why or why not?

If the membrane is suddenly permeable to Na⁺ and K⁺ to the same extent, then the only factor affecting the ions crossing the membrane is the concentration gradient between the external/internal environments. The ion with the greatest concentration differential would lose ions through the membrane at a faster rate until equilibrium is reached.