Relationship of the Cell Surface to 

 Electrolyte Metabolism in Yeast' 



ASER ROTHSTEIN 



University of Rochester, School of Medicine and 

 Dentistry, Rochester, New York 



IN CONSIDERING THE SUBJECT of the present symposium, '^ Electrolytes in 

 Biological Systems", as it applies to living cells, it is convenient to divide 

 the available material into two rather arbitrary categories: a) the action of 

 cells on electrolytes, and b) the action of electrolytes on cells. The first category 

 includes such phenomena as chemical interactions of cellular constituents with 

 electrolytes; binding of electrolytes by fixed structures of the cell; and the 

 transfer of electrolytes across membranes in the face of unfavorable activity 

 gradients. The second category includes all of the many manifestations of 

 biological activity which can be influenced by electrolytes such as growth, 

 metabolic rates, contraction, mobility and many others. The two categories 

 are not mutually exclusive. For example, an electrolyte may exert an effect on 

 the activity of the cell following its transport into the interior of the cell; or 

 one electrolyte may stimulate the metabolism of the cell, thereby increasing 

 the transfer of another electrolyte. 



Yeast cells constitute an excellent material for studying both the action of 

 electrolytes on the cell and the action of the cell on electrolytes. For example, 

 the yeast cell can, during active fermentation of glucose, transfer potassium 

 ion from the medium into the cell against an activity gradient as great as 5000 

 to I. At the same time it excretes hydrogen ion, also against a large activity 

 gradient. Yet the metabolism which supplies the necessary energy for these 

 transfers is itself markedly influenced by the potassium and hydrogen ion 

 concentration of the medium. 



^lany of the phenomena associated with electrolytes apparently involve the 

 cell membrane or the surface layer of the cell. Evidence will be presented 

 supporting the view that the surface layer of the cell contains some of the 

 enzymatic machinery of the cell which may supply, in whole or in part, the 

 energy required for the active transport of ions across the cell membrane. Also, 

 it is suggested that certain of the described effects of extracellular electrolytes 



' This report is based in part on work performed under contract with the United States 

 Atomic Energy Commission at the University of Rochester, Atomic Energy Project, Roch- 

 ester, N. Y. 



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