Final answer:
After hydrolyzing ATP, the Na-K ATPase pump changes conformation, allowing it to bind three Na+ ions, which are then released into the extracellular fluid. The pump then binds two K+ ions and returns to its original conformation.
Step-by-step explanation:
After the Na-K ATPase pump hydrolyzes ATP, the pump changes conformation. This conformational change allows the pump to bind three Na+ ions. The binding of these ions causes another conformational change, releasing the Na+ ions into the extracellular fluid. The release of Na+ ions triggers another allosteric change, after which two K+ ions are able to bind to the pump, leading to the release of the phosphate group from the pump protein and returning the pump to its original conformation.