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Osmosis is the process essential for many biological processes, including the absorption of nutrients and the regulation of water balance in cells and organisms. Osmosis plays a critical role in maintaining the proper functioning of biological systems, and understanding its principles is essential to many areas of science, including biology, chemistry, and biochemistry.



What is Osmosis?

Osmosis is the movement of molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane until equilibrium is reached. The Osmotic phenomenon was discovered in 1748 by Nollet. Osmosis takes place in specialized cells called root hair cells that have been modified to maximize the absorption of water and ions. These cells’ shape improves the amount of surface area that can be absorbed. Water and chemicals in the solution can easily pass through the cell walls of plants.

Osmotic Solution

Three types of osmotic solutions are present:

  • Hypotonic Solution: A solution in which solute concentration is high inside the cell than in the surrounding.
  • Hypertonic Solution: A solution in which solute concentration is high in the surrounding than the cell.
  • Isotonic Solution: A solution in which the solute concentration is equal both inside and in the surrounding.

Types of Osmosis

  • Endosmosis: or the movement of water molecules into the cell, takes happens when a cell is submerged in a hypotonic solution.
  • Exosmosis: the flow of water molecules out of a cell occurs when it is submerged in a hypertonic solution. In this cell turn flaccid or plasmolysis.

Effect of Osmosis on Cell

Cells are directly affected by osmosis. If plant and animal cell is surrounded by the hypotonic solution then the animal cell lyse. Plant cells don’t lyse because of the cell wall and plant cells need more water than animal cells. solution. Animal cells stabilize themselves in the isotonic solution, but plant cells in the isotonic solution remain no longer turgid.

The reverse of osmosis is possible by exerting some external pressure this process is known as reverse osmosis. External pressure is exerted on the solute side, as a result, the flow of the moment either stopped or is reversed. The minimum pressure needed to attain reverse osmosis is known as osmotic pressure.

Osmotic Pressure

Osmotic Pressure


It is the minimum pressure needed to stop the moment through the semipermeable membrane. The osmotic pressure depends on the concentration of the solute. Osmotic pressure is calculated by using the equation:

π = MRT

  • π=osmotic pressure
  • M=molar concentration of solutes
  • R=gas constant
  • T=Temperature

Significance of Osmosis

 The biological significance of osmosis includes the following:

  • Osmosis helps in maintaining the turgidity of cells.
  • Dehiciesnce of fruit and sporangia occurred with the help of osmosis.
  • High osmotic pressure helps the plant from drought.
  • Osmosis help in transpiration and excretion 
  • Osmosis helps the roots to absorb water and nutrients from the soil.
  • Osmosis stabilizes the internal environment of the cell by maintaining the water and intracellular fluids.
  • Uptake of many ions via cell because of osmosis.
  • Regulates the movement of plant cells.
  • It is required for cellular survival.
  • Osmosis plays an important role in seed germination.
  • Water molecules are moved between the cell and the cell organelles.
  • It is involved in moving water molecules from the soil into the root nodules in plants.
  • The mechanism of stomata is primarily due to the guard cells’ response to osmotic pressure in relation to the epidermal cells.

Examples of Osmosis

It plays an important role in both plant and animal cells. Osmosis help in 

  • Absorption of nutrients and water from the soil due to osmosis.
  • Osmosis help in the opening of the stomata. When the concentration of water increases the guard cell starts absorbing water and the guard cell swell which leads to opened stomata.
  • Humans suffer from diarrhea caused by cholera also because bacteria affect osmosis. When the bacteria number starts increasing they reverse the flow and the absorption of water decrease which leads to diarrhea.
  • Fingers become pruney when the hands are placed in water for a long time, due to which water flow inside the cell via osmosis.

Factors of Osmosis

  • Osmotic Pressure: Osmosis can be countered by increasing the pressure in the high solute concentration region relative to the low solute concentration region. The force per unit area, or pressure, required to prevent water (or any other high-liquidity solution) from passing through a selectively permeable membrane and into a solution of greater concentration is equal to the solution’s osmotic pressure, or turgor. Osmotic pressure is a colligative property, which means that it is affected by the concentration of the solute rather than its content or chemical identity.
  • Osmotic Gradient: The osmotic gradient is the concentration difference between two solutions on either side of a semipermeable membrane, and it is used to calculate the percentage concentration of a specific particle dissolved in a solution.

Variation of Osmosis

  • Osmosis (Reverse osmosis): Reverse osmosis is a separation process that employs pressure to force a solvent through a semi-permeable membrane that retains the solute on one side while allowing the pure solvent to pass to the other, forcing it from a region of high solute concentration through a membrane to a region of low solute concentration by applying pressure more significant than the osmotic pressure.
  • Forward Osmosis: Osmosis can be used directly to separate water from a solution containing undesirable solutes. A higher osmotic pressure “draw” solution than the feed solution is used to induce a net flow of water through a semi-permeable membrane, causing the feed solution to concentrate as the draw solution dilutes. The diluted draw solution can then be used directly (as with an ingestible solute such as glucose), or it can be sent to a secondary separation process to remove the draw solute.

Depending on the draw solute and the feedwater treated, this secondary separation may be more efficient than a reverse osmosis process alone. Forward osmosis research is ongoing, with a focus on applications in desalination, water purification, water treatment, food processing, and other fields.

FAQs on Osmosis

Q1: What is Osmosis?


The movement of solute from high concentration to lower through the semipermeable membrane such process is known as 

Q2: Is osmosis a passive or active process?


Osmosis is a type of passive transport because in this process no need for energy. Movement of solute occurs from higher concentration to lower concentration till they reach the equilibrium.

Q3: What is the difference between osmosis and diffusion?


Osmosis is the movement of solvents across a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration. Diffusion, on the other hand, does not require a semi-permeable membrane to occur, and molecules move from a region of higher concentration to a region of lower concentration.

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Last Updated : 27 Mar, 2023
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