Effects of erythrocyte lipid and of glucose and galactose concentration on transport of the sugars across a water-butanol interface.

A property of sugar transport into the human erythrocyte is that a sugar with a high affinity for the hypothetical "carrier" will enter the cell at low concentration more rapidly than a sugar with lower affinity for carrier. At high concentration the sequence will be reversed. This behavior is exemplified by glucose, which enters erythrocytes faster than galactose at 0.015 m and slower than galactose at 1.3 m. A physicochemical model with the same properties has been found: layers of butanol and water with erythrocyte lipid at the interface. With total lipid from the human erythrocyte incorporated into the model, glucose at low concentration enters the oil phase faster than galactose and at high concentration galactose enters more rapidly. In the absence of lipid, glucose flux exceeds galactose flux at all concentrations. The hypothetical carrier molecule has not been identified.