ASKK ROTHSTEIN 87 



during respiration. For example, at pH 2.6 the fermentation was increased 84% 

 and the respiration only 26%. Aerobic as well as anerobic fermentation was 

 stimulated by potassium resulting in an increase in RQ from 1.7 to 2.5 (table 8). 

 The monovalent cations can intluence the end products of fermentation 

 (fig. 11). For e.xample, in the range pH 2.0 to 7.0, the primary products of fer- 

 mentation are alcohol, Cih and polysaccharides, with small amounts of glyc- 

 erol. When the fermentation is stimulated by potassium or ammonium ion 

 at pH 7.0, there is a marked increase in glycerol production and a decrease in 

 polysaccharide formation (38, 49). 



Table 8. Effect of potassium on respiration and fermentation measured by gas 

 exchanges and glucose utilization 



Anaerobic CO2 

 Aerobic COj 

 Respiration (O2) 

 Aerobic fermentation* 

 R.Q. 



(All values are averages of 3 experiments) 



/imol/mg hr. /imol/mg hr. 



Aerobic glucose utilization 0.29 0.49 



Anaerobic glucose utilization 0.53 o-97 



(All values are averages of 2 experiments) 



* Aerobic fermentation is calculated by assuming an R.Q. of i.o for glucose respiration, 

 and thereby subtracting O2 consumption from aerobic CO2 production. 



t Baker's yeast always has a high aerobic fermentation, despite maximal shaking of the 

 flasks. R.Q.'s for untreated yeast vary from 1.2 to 1.8. 



The actions of the monovalent cations on metabolism are exerted on re- 

 actions occurring in the surface layer of the cell. This conclusion is based on a 

 number of observations. For example, in the experiments with H+, the pH 

 was altered over the range of 2.0 to lo.o. Despite the dramatic effects on the 

 rate of fermentation, the general level of the cytoplasmic pH did not change 

 appreciably during the experiments but remained at the level of 6.2 (49), as 

 determined by the freezing and thawing technique (8). The absence of interac- 

 tions between extracellular H"^ and the cytoplasmic contents is also indicated 

 by the fact that intact cells have only a small buffering capacity compared to 

 that of the cytoplasmic contents of disrupted cells. Finally, it has been found 

 that the respiration of endogenous stores, in contrast to the fermentation or 

 respiration of glucose, is almost unaffected by extracellular pH (i, 46), although 

 most of the enzymes involved, are themselves quite susceptible. The enzymes 

 of endogenous respiration are located in a cellular compartment which is 

 sheltered from the extracellular pn, whereas some of the reactions in sugar 



