Quiz 1 Question : Why is it possible for potassium to diffuse easily into and out of cells? Student Answer: Potassium has a greater concentration in the ICF. Sodium has a greater concentration in the ECF. The resting plasma membrane is more permeable to potassium. An excess of anions is inside the cell. Instructor Explanation: Because the resting plasma membrane is more permeable to K+ than to Na+ , K+ can easily diffuse from its area of higher concentration in the ICF to its area of lower concentration in the ECF. Because Na+ and K + are both cations, the net result is an excess of anions inside the cell, resulting in theresting membrane potential. The remaining options do not correctly identify the process that most easily diffuses K+ .