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Ion Behavior in Yeast. III. Specificity, Anomalous Cation Efflux, and Role of Metabolism¹

ABSTRACT

In this communication we consider a simple and novel hypothesis for preferential efflux of Na⁺ and H⁺ from the yeast cell (Saccaromyces cerevisiae Meyer ex Hansen) against an apparent electrochemical potential gradient. Attention is centered upon the peripheral membrane of the cell which is of high lipid content and of correspondingly low dielectric constant. As respiration proceeds, waste products X^- (predominantly succinate) continuously move from the cell via the membrane, thereby unavoidably providing a driving force for cation efflux. The accompanying cations are considered to form undissociated ion pairs with X^- in the membrane. Coulombic attraction accordingly favors the smaller cation and is presumed to account for the specificity for Na⁺ over K⁺, e.g., in the efflux process. The hypothesis thereby accounts for anomalous ion behavior without postulation of specially endowed transport pumps and without expenditure of energy by the cell.

¹ Technical contribution no. 797, Chemistry Dept., Montana State University, Bozeman, Mont. Partially supported by a grant from the National Science Foundation.

² Professor.

Received for publication August 6, 1968. Accepted for publication January 14, 1969.