Final answer:
Potassium (K+) is the major intracellular cation with concentrations approximately 30 times higher inside cells than outside, while the sodium-potassium pump maintains this gradient using ATP.
Step-by-step explanation:
The major intracellular cation that is present at higher concentrations inside cells as compared to its concentration outside is potassium (K+). Normally, potassium levels are about 30 times higher inside cells than outside, making it a critical element for maintaining cellular functions and the resting membrane potential of cells.
In contrast, sodium (Na+) ions have a higher concentration outside of the cell, about 10 times more than inside. The sodium-potassium pump is responsible for maintaining these concentration gradients by actively moving sodium out of the cell and potassium into the cell. This activity is crucial as it helps to establish a net negative charge inside the cell compared to the outside. The sodium-potassium pump uses ATP to transport ions against their concentration gradients, pumping two potassium ions into the cell while removing three sodium ions per ATP molecule consumed.