Two-carrier models for mediated transport. II. Glucose and galactose equilibrium exchange experiments in human erythrocytes as a test for several two-carrier models.

1. Equilibrium exchange of glucose and of galactose is measured in human erythrocytes over wide concentration ranges. One-site Michaelis-Menten-type kinetics are shown for the two sugars. 2. In view of the results, two of the two-carrier models discussed in paper I (Eilam, Y. (1975) Biochim. Biophys. Acta 401, 349-363), the different sequential carriers and the antiparallel simultaneous carriers, are rejected for the sugar transfer system. The antiparallel sequential carriers model is consistent with these results.