The sodium-potassium pump maintains high concentrations of Na⁺ outside the cell and K⁺ inside the cell, against their concentration gradients.

1. 3 cytoplasmic Na⁺ bind to the pump.

2. ATP donates a phosphate group for energy.

3. The protein changes its shape, expelling Na⁺ to the outside.

4. 2 extracellular K⁺ bind to the pump, releasing the phosphate.

5. The pump resumes its original shape.

6. K⁺ is released inside.

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