TRANSPORT MECHANISMS A CROSS
THE CELL MEMBRANE
The main function of the cell membrane is selective permeability and transport of various ions and substance into and out of the cell this movement across the cell membrane may occur with or without the assistance of membrane components the process of transport that occurs without assistance of membrane
components is called passive transport or non mediated transport it includes diffusion and osmosis the process of transport that occurs with the assistance of membrane components is called mediated transport facilitated diffusion and active transport are mediated transport mechanisms a third type of process of transport involves the formation and movement of membrane bound sacs or vesicles this is known as vesicle mediated transport endocytosis (pinocytosis and phagocytosis )and exocytosis are the examples of such transport system
PASSIVE TRANSPORT ;
it is always unsaturable non selective and energy indepentant 1.diffusion is the random spreading of the molecules or ions in fluids or gases due to activity within their atomic structure its rate is directly related to difference in concentration gradient across the cell membrane area of the membrane and temperature at which the process takes place diffusion is inversely related to the square root of the molcular weight of the substance and the thickness of the membrane the rate of
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