The effect of diffusible acids on potassium ion uptake by yeast

1. When yeast oxidizes ethanol at different pH values the uptake of K(+) corresponds closely to the amount of acetate accumulated at each pH value. 2. The addition of semicarbazide to the suspension buffered at pH4.75 inhibited both the K(+) uptake and the acetate accumulation by about 50%. 3. The addition of either acetate or propionate to the suspensions markedly increased the K(+) uptake. 4. The addition of acetate to the suspensions lowered the intracellular pH of the yeast from a resting value of pH5.80 to 5.56. 5. The ratio of the initial rate of K(+) uptake to O(2) consumption was 0.77. This ratio was increased to 1.77 in the presence of 10mmol of propionate/l.