. Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954. Electrophysiology; Electrolytes; Electrolytes; Electrophysiology; Physiology, Comparative. ASER ROTHSTEIN 77 in order to fully characlerize the phenomenon. If further experiments do vali- date the asymptotic relationship between K+ inflow and K+ concentration, then it might be assumed that the data represent an interaction between K+ and a cellular constituent which is a part of the ion transport system. It has already been
. Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954. Electrophysiology; Electrolytes; Electrolytes; Electrophysiology; Physiology, Comparative. ASER ROTHSTEIN 77 in order to fully characlerize the phenomenon. If further experiments do vali- date the asymptotic relationship between K+ inflow and K+ concentration, then it might be assumed that the data represent an interaction between K+ and a cellular constituent which is a part of the ion transport system. It has already been pointed out in a previous section that K+ forms a complex with certain sites located on the outer surface of the cell. The question then arises concerning the possible identity of these sites with those whose existence is suggested by the kinetics of the transport. Fortunately, it is possible to prevent interaction of K+ with the binding sites of the cell surface by adding appropriate concentrations of bivalent cations. The latter, because of their much greater affinity for the binding sites will completely displace K+. The uptake of K+ in. 10 20 30 40 50 60 Fig. 7. Effect of Mg^^ on the removal of K^ from the medium by actively metaboHzing yeast cells. 4 0 K-. « CONTROL V VSr*^.- â⢠35 PH "V ^^ â 1 _^__L,CI *\ ^-4 t: ^--â¢.iif^l 30 ^^^^ âº-^ -â¢^KCl ^ -,,_ 25 - TIME IN MINUTES 1 ' 1 Lâ Fig. 8. Changes in the pH of the medium during fermentation of glucose, as influenced by various ions. the presence of Mg"*"^ proceeds at a rate which is only a little slower than that in its absence, despite the fact that the concentration of Mn++ is sufficiently high to displace virtually all of the K+ from the cell surface (fig. 7). Thus it must be concluded that the K+ binding sites which have been discussed previ- ously (page 72), play no essential role in K+-transport. Any interaction between K+ and the transport system must occur in a location inacces
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