Final answer:
One molecule of ATP can move approximately three and a half sodium ions across the cell membrane via the sodium-potassium pump, although the process operates with whole numbers, resulting in the movement of three sodium ions per ATP molecule.
Step-by-step explanation:
The sodium-potassium pump, an essential mechanism in animal cells, uses energy derived from the hydrolysis of ATP to transport sodium (Na+) and potassium (K+) ions against their respective concentration gradients. Specifically, it moves three Na+ ions out of the cell and two K+ ions into the cell, helping to maintain the electrochemical gradient necessary for various cellular processes. The hydrolysis of one ATP molecule releases 7.3 kcal/mol of energy. Given that it requires 2.1 kcal/mol of energy to move one Na+ ion across the cell membrane, a single ATP molecule's hydrolysis can move about three and a half Na+ ions. However, this process works in whole numbers, so effectively, one ATP molecule enables the movement of three Na+ ions across the membrane.