For more information about membrane proteins visit the Medical Biochemistry site at the University of Kansas Medical Center. Water Potential Water potential is directly proportional to the concentration of water molecules. Water molecules will move spontaneously from high to low water potential. Hydrostatic potential Hydrostatic potential is the potential needed to stop water from diffusing. The higher the temperature the more rapid the diffusion.
Efficient diffusion requires small distances and a high potential gradient.
Dialysis Dialysis is the diffusion of molecules of solute through a membrane. Molecules that diffuse freely across membranes are small and nonpolar. Examples include water, glycerol, and urea. Polarity and electrical charge also determine the degree of permeability. Most ions cannot traverse the membrane without help.