The document discusses factors that affect the rate of diffusion across cell membranes. It outlines that the rate of diffusion is affected by the concentration gradient of the substances, the partition coefficient which determines solubility in different mediums, the diffusion coefficient which depends on molecule size and medium viscosity, and the thickness and surface area of the membrane. Diffusion of electrolytes can involve facilitated diffusion, primary and secondary active transport, cotransport, or countertransport. The rate is also influenced by saturation of carrier protein binding sites, stereospecific binding, and competition between chemically similar substances.
