Final answer:
Potassium (b) is the ion that is found at higher concentrations in the intracellular fluid than in the extracellular fluid due to the action of sodium-potassium pumps in the cell membrane.
Step-by-step explanation:
The ion you would expect to find more in the intracellular fluid compartment than in the extracellular fluid compartment is potassium (b) Potassium. Sodium (Na+), calcium (Ca2+), and chloride (Cl-) are generally found at higher concentrations in the extracellular fluid (ECF). This balance of ions between the intracellular and extracellular compartments is crucial for various physiological functions, including the establishment of the resting membrane potential in neurons and muscle fibers, and the maintenance of osmotic pressure and pH balance.
Potassium is the major intracellular cation and plays a key role in maintaining the resting membrane potential as well as in membrane depolarization during action potentials. The high levels of potassium within cells and the low levels of sodium are maintained by sodium-potassium pumps, which actively transport sodium out of the cell and potassium into the cell, utilizing ATP as an energy source.