Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954 electrolytesinbi00shan Year: 1955 62 ELECTROLYTES IN BIOLOGICAL SYSTEMS of potassium and the secretion of sodium, that these mechanisms are inde- pendent of each other, and that they are energized by the metaboHc degrada- tion of carbohydrate (fig. 21). Any comparison between Ulva and Valonia must take cognizance of the morphological differences between the cells of the two organisms. In the rela- tively small cells of Ulva t
Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954 electrolytesinbi00shan Year: 1955 62 ELECTROLYTES IN BIOLOGICAL SYSTEMS of potassium and the secretion of sodium, that these mechanisms are inde- pendent of each other, and that they are energized by the metaboHc degrada- tion of carbohydrate (fig. 21). Any comparison between Ulva and Valonia must take cognizance of the morphological differences between the cells of the two organisms. In the rela- tively small cells of Ulva the cytoplasmic mass is large relative to the amount of fluid in the vacuole, while in Valonia cells the opposite situation pertains, by far the greater portion of the mass is vacuole with the cytoplasm con- tributing only a very small part. There are three obvious consequences of these relationships which must be considered in comparing the two forms. First, in Ulva one analyzes largely the cytoplasmic fluid, while in Valonia the cyto- plasm contributes little to whole-cell analyses. Secondly, in Valonia the major fraction of the analyzed ions has passed through two living membranes. Finally, RADIANT L ENERGY I STORED CARBOHYDRATES 3-PHOSPHOGLYCERALDEHYDE 3-PHOSPHOGLYCERIC ACID PHENYLURETHANE DNC PHENYLURETHANE DNC ENERGY- . UTILIZING , No+ ^.MECHANISMS ^j\<^ ''''^ fu^ CELL 'MEMBRANE' DIFFUSION ^ M«17 ^K'^ 'DIFFUSION Fig. 21. Diagrammatic representation of the interpretation of the data presented above. the ratio of total exterior surface to total mass is much greater in Ulva than in Valonia. These last two factors are important in kinetic studies and may prob- ably be at least partly responsible for the rather sluggish responses of Valonia to metabolic inhibitors contrasted with the more rapid responses in Ulva. There also exists the possibility that the Valonia membranes are less permeable to ions of sodium and potassium than is the Ulva membrane. Regardless of th
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