Final answer:
Potassium is more concentrated inside the cell due to the action of the sodium-potassium pump, which uses ATP to create a high internal potassium concentration and contributes to the cell's resting membrane potential.
Step-by-step explanation:
Potassium is more concentrated inside the cell than other cations such as sodium and calcium. This is largely due to the sodium-potassium pump, which actively transports three sodium ions out of the cell for every two potassium ions it moves in, utilizing ATP as the energy source. This process creates a high internal concentration of potassium and contributes to the resting membrane potential. Moreover, the inside of the cell is slightly negatively charged compared to the outside, providing an additional force that tends to move sodium into the cell rather than potassium. Potassium can leak through channels in the cell membrane, which are open a significant amount of time, but the pumps maintain the overall concentration gradient.