Na+/K+ ATPase

[akbyst2]

The Na+/K+ ATPase (the sodium pump) moves 3Na+ out of and 2K+ into cell cytoplasm. Each ion moves up its electrochemical gradient. In a normal cell, why don't Na+ ions enter and K+ ions leave the cell (each going down its concentration gradient) by way of this transporter? Explain in detail the characteristics of this active transporter that preclude reverse flow of the ions under normal cellular conditions.

HINT: There are two different reasons why the transporter cannot run in the reverse direction. You need to consider both to get full credit.

[JackBean]

I would guess different affinity for each ion in both stages and phosphorylation

[vinayaksabnis]

According to me,
Sodium inside the cell binds to the protein the addition of the phosphate group from ATP changes the shape of the protein and the sodium is expelled now potassium binds to the protein the phosphate is released and the protein is returned to its owner shape then the potassium is moved into the cell sodium can once again can bind to the protein and the process repeats as long as there is a supply of ATP...

[JackBean]

that's nice, but why it goes in this order?

[vinayaksabnis]

I think inside a cell this order keeps repeating making exchange of ions...