The low-affinity component of the glucose transport system in Saccharomyces cerevisiae is not due to passive diffusion.

It has been claimed that the low-affinity component of glucose transport in Saccharomyces cerevisiae is due to passive diffusion of the sugar across the plasma membrane. We have investigated this possibility. For this purpose we have measured the permeability coefficient of hexoses in this organism. We have found that this coefficient is at least two to three orders of magnitude lower than required to account for the low-affinity component of glucose transport, and have concluded that this component is not due to passive diffusion.