Osmosis, Diffusion, Hypotonic solution, isotonic solution and hypertonic solution

Define osmosis.

The movement of water from a region of high concentration to a region of low concentration through a semi permeable membrane is known as osmosis.

What is diffusion?

The movement of gases (like carbon dioxide and oxygen) from a region of high concentration to a region of low concentration through a semi permeable membrane is known as diffusion. Thus, diffusion plays an important role in gaseous exchange between the cells as well as the cell and its external environment.

What is a 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.

What is a 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.

What is a 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. Again, water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink.