The document discusses cell membranes and various methods of transport across membranes. It summarizes that cell membranes function to protect cells, control substances moving in and out, and maintain ion concentrations. The three main methods of transport across membranes are diffusion, osmosis, and active transport. Diffusion is the passive movement of molecules from high to low concentration, while osmosis is the passive transport of water across membranes. Active transport requires energy to transport molecules against a concentration gradient using ATP. The document then outlines experiments using dialysis tubing and solutions to demonstrate these transport methods.