OSMOTIC PRESSURE

Osmotic pressure

       
  • As a result of the separation of two solutions by the semi permeable membrane, a pressure is developed in solutions due to the presence of dissolved solutes in it. This is called as osmotic pressure (OP). OP is measured in terms of atmospheres and is directly proportional to the concentration of dissolved solutes in the solution. More concentrated solution has higher OP. The OP of a solution is always higher than its pure solvent.
  • During osmosis, the movement of solvent molecules takes place from the solution whose osmotic pressure is lower i.e., less concentrated or hypotonic into the solution whose osmotic pressure is higher i.e., more concentrated or hypertonic.
  • Osmotic diffusion of solvent molecules will not take place if the two solutions separated by the semi permeable membrane are of equal concentration having equal osmotic pressures (i.e., they are isotonic). In plant cells, plasma membrane and tonoplast act as selectively permeable or differentially permeable membrane. Depending on this, the solution have been classified as;
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    • Hypertonic solution: A solution having a concentration such that it gains water or solvent by osmosis across a semi-permeable membrane from some other solution is termed as hypertonic solution (more concentrated solution)
    • Hypotonic solution: A solution having a concentration such that it loses water or solvent by osmosis across a semi-permeable membrane to some other solution is termed as hypotonic solution (less concentrated solution)
    • Isotonic solution: A solution having a concentration such that it neither gains nor loses water or solvent by osmosis when separated by a semi permeable membrane from another solution is termed as isotonic solution
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Last modified: Wednesday, 24 August 2011, 8:59 AM