The difference between the concentration of a substance between two areas is called the concentration gradient. This concentration gradient between a cell and its environment shows a difference resulting in the simplest form of transport called the passive transport. It is the movement of substances from a region of its higher concentration to a region of its lower concentration along with the concentration gradient across a semi permeable membrane.
Passive transport includes diffusion, facilitated diffusion, osmosis and filtration. All these processes are involved in various metabolic activities of the cell. Some of the examples are the movement of water molecules, nutrients, elimination of waste substances, exchange of gases and important life processes like digestion, respiration, excretion, transmission of nerve impulses and others depend on different types of passive transport. On elimination of concentration gradient between a cell and its environment, all the metabolic activities of the cell are inhibited and the cell dies.
