This document discusses an experiment to demonstrate how membrane composition affects an element's rate of diffusion. It is hypothesized that methylene blue will diffuse more slowly than potassium permanganate due to size differences. It is also hypothesized that a water tube in sucrose will decrease in volume while a sucrose tube in water will increase in volume, demonstrating osmosis. A starch-filled tube is expected to change color from iodine, while a water and iodine solution will remain the same color, showing starch is not permeable. The background provided discusses how cell membranes act as selective barriers regulating cellular transport.