Question: Passive transport is the movement of molecules across the cell membrane without the use of cellular energy such as ATP. It occurs naturally from an area of higher concentration to an area of lower concentration, following the concentration gradient until equilibrium is reached. There are different types of passive transport, including simple diffusion, where molecules move directly through the membrane; osmosis, which is the movement of water; and facilitated diffusion, where proteins help larger or charged molecules cross the membrane. Just one tiny tiny tiny sentence in it. Need Assignment Help?