The accumulation of ions in living cells-a non-equilibrium condition

Abstract

1. Living cells ofValonia macrophysaKutz were exposed for different lengths of time to sea water in which the proportion of potassium had been increased or decreased by the addition of isotonic KC1 or NaCl solutions. 2. The concentration of potassium in the sap ordinarily increased more than that of sodium or chloride regardless of whether it was present in more or less than normal concentration in the surrounding solution. 3. The chloride concentration in the sap ordinarily changed in much the same way as the potassium concentration, but to a significantly smaller extent. 4. The sodium concentration appears to have first increased and then decreased, depending upon the length of exposure and the extent to which the sea water was altered. 5. This may be explained by supposing: (a) the cell to be normally in a non-equilibrium condition with respect to the surrounding solution; (b) to be surrounded by a plasma membrane consisting of a mosaic of anion-permeable and cation-permeable areas which are of the nature of charged porous films, and as such exaggerate differences between the diffusion velocities of the ions to which they are permeable; (c) that the diameters of the pores are variable according to experimental conditions; (d) that the penetrabilities of different ions are characteristic functions of their own effective diameters and of the diameters of the pores in the membranes. 6. This theory is shown to explain more or less completely also the intake of ions by plants, the changes in morphology of green algae grown in darkness, the characteristic ion content of erythrocytes and of neoplastic cells, and the relation between glycolysis and growth of neoplasms.