Passive transport is the movement of molecules across the cell membrane without the expenditure of cellular energy (ATP). This process relies on the concentration gradient, moving substances from areas of higher concentration to areas of lower concentration.
Types of Passive Transport
Simple Diffusion: Molecules move directly through the phospholipid bilayer. Small, nonpolar molecules like oxygen and carbon dioxide typically use this method. Facilitated Diffusion: Involves transport proteins such as carrier proteins and channel proteins. Larger or polar molecules, such as glucose and ions, use facilitated diffusion. Osmosis: A specific type of facilitated diffusion that involves the movement of water molecules across a semipermeable membrane through aquaporins.
