At 37 °C the equilibrium concentration of inside a cell is 0.085 M and outside is 0.026 M. The cell membrane is permeable to and . The only ion present in addition to and is a protein (Prin+/–) inside the cell. The protein holds a single positive or negative charge. The is at equilibrium across the membrane while the protein is inside the cell and cannot permeate the membrane. What is the concentration of Prin+/– (in M)?
