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 C. ADRIAN M. HOGBEN 199 If a postulate is introduced that there exists within the complex membrane a region or micelle whose pH is maintained distinctively different from that of the external bathing solutions, and if the boundaries of that region differ ap- preciably in their relative permeability to ionized and unionized particles (fig. 3b), there will be a net flux of a weak electrolyte i
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 C. ADRIAN M. HOGBEN 199 If a postulate is introduced that there exists within the complex membrane a region or micelle whose pH is maintained distinctively different from that of the external bathing solutions, and if the boundaries of that region differ ap- preciably in their relative permeability to ionized and unionized particles (fig. 3b), there will be a net flux of a weak electrolyte independent of the pH of the external bathing solutions. Across the face of the micelle that is relatively impermeable to ions, there will be net movement till a steady state concen- tration difference is attained, as depicted in figure 3a. However, across the JU. .Hi Ac ds (b) Bases Fig. 3. Micellar model of weak electrolyte distribution, a: Osterhout's model of the steady state distribution of a weak acid, pKa 4, across a cell membrane separating two solutions of difTerent pH, the cell membrane being freely permeable to the unionized moiety, b: A trans- port micelle whose interior pH differs from that of the external bulk solution and of whose boundaries that on the left is freely permeable to unionized particles (light arrow) and that on the right is equallj' permeable to both unionized and ionized (dark arrow) particles. The movement and distribution across the left boundarj^ would correspond to the oil barrier of a developing a concentration gradient while the free movement across the right boundary would tend to dissipate the concentration dififerences developing on the left, such that weak acids would be pumped from right to left and weak bases from left to right. opposite face of the micelle which does not discriminate between ionized and unionized particles, there will be net movement tending to dissipate the con- centration difference building up across the other
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