A focus gradient is alleviated through diffusion, nevertheless membranes can hinder diffusion and maintain a concentration gradient.?Concentration? refers to the amount of a solute is within a granted number of solvent. A corner of the water tank which includes just experienced salt dumped into it could have a very much increased concentration of salt than the opposite close belonging to the tank, the place no salt has diffused to. For this reason, a focus gradient is alleged to exist while in the tank.