passive transport
PASSIVE TRANSPORT IS A MOVEMENT OF BIOCHEMICALS AND OTHER ATOMIC OR MOLECULAR SUBSTANCES ACROSS CELL MEMBRANES WITHOUT NEED OF ENERGY INPUT. UNLIKE ACTIVE TRANSPORT, IT DOES NOT REQUIRE AN INPUT OF CELLULAR ENERGY BECAUSE IT IS INSTEAD DRIVEN BY THE TENDENCY OF THE SYSTEM TO GROW IN ENTROPY. THE RATE OF PASSIVE TRANSPORT DEPENDS ON THE PERMEABILITY OF THE CELL MEMBRANE, WHICH, IN TURN, DEPENDS ON THE ORGANIZATION AND CHARACTERISTICS OF THE MEMBRANE LIPIDS AND PROTEINS. THE FOUR MAIN KINDS OF PASSIVE TRANSPORT ARE SIMPLE DIFFUSION, FACILITATED DIFFUSION.THERE ARE THREE FORMS OF PASSIVE TRANSPORTS. DIFFUSION, OSMOSIS, AND FACILITATED DIFFUSION. DIFFUSION IS THE NET MOVEMENT OF IONS OR MOLECULES FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION UNTIL EQUILIBRIUM IS REACHED. TEMPERATURE AND PRESSURE – THE RATE OF DIFFUSION INCREASES WITH INCREASED TEMPERATURE AND PRESSURE. OSMOSIS ISTHE MOVEMENT OF WATER FROM AN AREA OF HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION, ACROSS A SEMI-PERMEABLE MEMBRANE UNTIL EQUILIBRIUM IS REACHED. FACILITATED DIFFUSION IS THE PROCESS OF DIFFUSION THAT IS MEDIATED BY A MEMBRANE PROTEIN.FACILITATED DIFFUSION IS THE PROCESS OF SPONTANEOUS PASSIVE TRANSPORT OF MOLECULES OR IONS ACROSS A CELL'S MEMBRANE VIA SPECIFIC TRANSMEMBRANE INTEGRAL PROTEINS. ENERGY IS NOT REQUIRED. Passive transport is the cellular process of moving molecules and other substances across membranes. Passive transport differs from active transport in that it does not involve any chemical energy. Rather, passive transport relies on the innate permeability of the cell membrane and its component proteins and lipids. Other kinds of particles can also move through the cell membrane as well.