The concentration of potassium K+ ions in the internal sap of a plant cell (for example) a fresh water alga) may exceed by a factor of l04 the concentration of K+ ions in the pond water in which the cell is growing. The chemical potential of the K+ ions is higher in the sap because their concentration n is higher there. Estimate the difference in chemical potential at 300K and show that it is equivalent to a voltage of 0.24 V across the cell wall. Take μ as for an ideal gas. Because the values of the chemical potentials are different, the ions in the cell and in the pond arc not in diffusive equilibrium. The plant cell membrane is highly impermeable to the passive leakage of ions through it. Important questions in cell physics include these: How is the high Concentration of ions built up within the cell? How is metabolic energy applied to energize the active ion transport?