Final answer:
The ATP molecule transfers a phosphate group to the sodium-potassium pump, which is crucial for the pump's function in transporting ions across the cell membrane.
Step-by-step explanation:
The ATP molecule transfers a phosphate group to the sodium-potassium pump, which is vital for its operation. During the pumping cycle, three sodium ions (Na+) bind to the pump and an ATP molecule provides energy by transferring one of its phosphate groups to the pump. This phosphorylation triggers a conformational change in the pump, releasing the sodium ions outside the cell. Subsequently, two potassium ions (K+) bind to the pump, which causes a shape change allowing the release of the phosphate group and the movement of potassium ions into the cell.