What is Osmosis?

Osmosis is a passive process and happens without any expenditure of energy. It involves the movement of molecules from a region of higher concentration to lower concentration until the concentrations become equal on either side of the membrane. It is a vital process in biological systems, as biological membranes are semipermeable. In general, these membranes are impermeable to large and polar molecules, such as ions, proteins, and polysaccharides, while being permeable to non-polar or hydrophobic molecules like lipids as well as to small molecules like oxygen, carbon dioxide, nitrogen, and nitric oxide.

Types of Osmosis

  • Endosmosis: When a substance is placed in a hypotonic solution, the solvent molecules move inside the cell and the cell becomes turgid or undergoes deplasmolysis. This is known as endosmosis.
  • Exosmosis: When a substance is placed in a hypertonic solution, the solvent molecules move outside the cell and the cell becomes flaccid or undergoes plasmolysis. This is known as exosmosis.


Importance of Osmosis

  • It influences the transport of nutrients and the release of metabolic waste products.
  • Osmosis is responsible for the absorption of water from the soil and conducting it to the upper parts of the plant through the xylem.
  • Stabilizes the internal environment of a living organism by maintaining the balance between water and intercellular fluid levels.
  • Maintains the turgidity of cells.
  • It is a process by which plants maintain their water content despite the constant water loss due to transpiration.
  • This process controls the cell-to-cell diffusion of water.
  • Osmosis induces cell turgor which regulates the movement of plants and plant parts.
  • Osmosis also controls the dehiscence of fruits and sporangia.
  • Higher osmotic pressure protects the plants against drought injury.

Osmotic Solutions

  • An isotonic solution has the same concentration of solutes both inside and outside the cell.
  • A hypertonic solution has a higher solute concentration outside the cell than inside.
  • A hypotonic solution is the one that has a higher solute concentration inside the cell than outside.

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