In this way, although the concentration of the solute may actually be different on both sides of the membrane, the availability of the solute is reduced in one of the compartments to such an extent that, for practical purposes, no gradient exists to drive transport.
Deste modo, aínda que a concentración do composto sexa realmente diferente a ambos os lados da membrana, a súa dispoñibilidade reducida nun dos compartimentos pode facer que, a efectos prácticos, non exista un gradiente que favoreza o transporte.