Osmosis in Cell || The Fundamental Unit of Life - 4 || for Class 9 in Hindi

In this Science (Biology) video in Hindi for class 9th we explained how osmosis happens in a cell through the cell membrane. We also explained what hypotonic, hypertonic and isotonic solutions are. This is a topic from Chapter 5 - 'The fundamental unit of life' of science from NCERT.

Osmosis is the spontaneous net movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, which tends to equalize the solute concentrations on the two sides.

As we know after washing clothes our fingers shrink due to the loss of water from the tissues. This happens due to osmosis.

We can observe the occurrence of osmosis with an egg.

Remove the shell of an egg by dissolving it in dilute hydrochloric acid. The shell is mostly calcium carbonate. A thin outer skin now encloses the egg. Put the egg in pure water and observe after 5 minutes. The egg swells because water passes into it by osmosis.
Place a similar de-shelled egg in a concentrated salt solution and observe for 5 minutes. The egg shrinks. Water passes out of the egg solution into the salt solution because the salt solution is more concentrated.

Hypotonic solution :- If the medium surrounding the cell has a higher water concentration than the cell, meaning that the outside solution is very dilute, the cell will gain water by osmosis. Such a solution is known as a hypotonic solution. Water molecules are free to pass across the cell membrane in both directions, but more water will come into the cell than will leave. The net (overall) result is that water enters the cell. The cell is likely to swell up.

Isotonic solution :- If the medium has exactly the same water concentration as the cell, there will be no net movement of water across the cell membrane. Such a
solution is known as an isotonic solution. Water crosses the cell membrane in both directions, but the amount going in is the same as the amount going out, so there is no overall movement of water. The cell will stay the same size.

Hypertonic solution :- If the medium has a lower concentration of water than the cell, meaning that it is a very concentrated solution, the cell will lose water by osmosis. Such a solution is known as a hypertonic solution.

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🔴 Click here to watch the whole playlist on Chapter 5 : 'The Fundamental Unit of Life' for Class 9 :
   • The Fundamental Unit of Life (Introduction...  

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Previous videos -

The Fundamental Unit of Life (Introduction)
   • The Fundamental Unit of Life (Introduction...  

Cell Membrane
   • Cell Membrane || The Fundamental Unit of L...  

Osmosis and Diffusion
   • Osmosis and Diffusion || The Fundamental U...