carrier- meditated diffusion 百 1 Vmax simple diffusion KM concentration of→ transported molecule Figure 11-7 Kinetics of sim ple diffusion com pared to carrier-mediated diffusion. Whereas the rate of the former is always proportional to the solute concentration, the rate of the latter reaches a maximum( Vmax when the carrier protein is saturated. The solute concentration when transport is at half its maximal value approximates the binding constant (KM) of the carrier for the solute and is analogous to the Km of an enzyme for its substrate. The graph applies to a carrier transporting a single solute; the kinetics of coupled transport of two or more solutes(see text) are more complex but show basically similar phenomenaFigure 11-7 Kinetics of simple diffusion compared to carrier-mediated diffusion. Whereas the rate of the former is always proportional to the solute concentration, the rate of the latter reaches a maximum (Vmax) when the carrier protein is saturated. The solute concentration when transport is at half its maximal value approximates the binding constant (KM) of the carrier for the solute and is analogous to the KM of an enzyme for its substrate. The graph applies to a carrier transporting a single solute; the kinetics of coupled transport of two or more solutes (see text) are more complex but show basically similar phenomena