FUNCTION OF PLASMA MEMBRANE

• Plasma membrane is a selective permeable membrane that means it allow to pass some specific molecules only inside the cell or outside the cell.
• The transportation of molecules through plasma membrane  is done by the process of osmosis and diffusion and some biological and physiological activities such as active transport.

DIFFUSION

The spontaneous movement of substance from higher concentration to lower concentration until it achieve its equilibrium condition.

Equilibrium condition means concentration is equal everywhere.

Some small substances like oxygen carbon dioxide , water etc passes through plasma membrane by the process of diffusion.

OSMOSIS

The spontaneous movement of solvent from higher concentration to lower concentration through semi or selective permeable membrane until it achieve its equilibrium condition is called osmosis.

• Cell absorb water through the process of osmosis.

If the cell ( animal cell and plant cell) put in the solution of water and salt or water and sugar.

following three things can be observe:-

1. If the concentration of water in solution is greater than concentration of water in the cell then water is absorb by the cell by the process of osmosis.

• The solution through which water is absorbed by the cell that type of solution is known as hypotonic solution.
• In this case cell will swell up.

    2.If the concentration of water in solution is equal to the concentration of water in the cell then no net movement of water takes place.

• The solution through which no net movement of water can takes place by the cell or in the cell, this type of solution is known as isotonic solution.
• In this case nothing is happen in the cell.

    3.If the concentration of water in solution is less than concentration of water in the cell then water is released by the cell by the process of osmosis.

• The solution in which the water from cell is released in the solution is known as hypertonic solution.
• In this case cell will shrink.
• The shrinking of cell through the process of osmosis the plant cell is said to be plasmolysed and animal cell is said to be crenated.

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