Passive transport is a type of cellular transport that does not require the use of energy to move substances (i.e., ions and molecules) across biological membranes. Passive transport uses concentration gradients to move substances across cell membranes, thereby transporting them from regions of high concentration to regions of low concentration. Passive transport can be divided into 1-osmosis (i.e., movement of solvents), 2-diffusion (i.e., movement of solutes), and 3-facilitated diffusion (i.e., movement of molecules with help of protein channels or carriers), and 4-filtration (i.e., movement of water by using a pressure gradient).
