Osmosis: introduction, types and significance

  • It is a special type of diffusion, which involves the movement of water through a semi-permeable membrane (differentially permeable membrane).
  • The movement of molecules takes place from the region of higher concentration of water (dilute solution) to the region of lower concentration of water (stronger solution) until the equilibrium.
  • It can also be defined as the movement of water or solvent from its higher chemical potential to its lower chemical potential through a semi-permeable membrane.
  • The free energy per mole of any substance in a chemical system is referred to as its chemical potential.
  • The higher the chemical potential of a substance, the greater will be its tendency to undergo chemical reactions, including processes like diffusion and osmosis.
  • The membrane which allows the movement of water molecules and certain solutes but holds back the large solute particles is called semi-permeable membrane.
  • For examples: plasma membrane, egg membrane, parchment paper, fish bladder, animal bladder, etc.

Types of osmosis

Osmosis can be classified into two types. They are:


  • When a living plant is placed in a solution having high osmotic pressure (hypertonic solution) than that of the cell sap, the water molecules move outward from the cell. The outward movement of water from a cell under the influence of concentrated solution is called ex-osmosis.

osmosisको लागि तस्बिर परिणाम    osmosisको लागि तस्बिर परिणाम


  • The osmotic entry of water inside the cell, when it is placed in a hypotonic solution is called endosmosis.
  • A solution having low osmotic potential in comparison to the other is said to be hypotonic solution, while a solution having higher osmotic potential is said to be hypertonic solution.
  • The solutions having the same osmotic potential are termed as isotonic solutions.

सम्बन्धित छवि     types of osmosisको लागि तस्बिर परिणाम



सम्बन्धित छवि       significance of osmosisको लागि तस्बिर परिणाम

  • Plant absorbs water from the soil solution by osmosis.
  • The cell to cell movement of water within the plant body is performed by osmosis.
  • The turgor pressure of cells resulting from osmosis maintain the definite shape and turgidity of living cells mainly in soft organs like fruits, leaves, young stems , etc.
  • It is also responsible for the growth of radical and plumule during seed germination as it is the source of the forces used by growing tissues.
  • It plays a key role in the penetration of young roots into the soil.
  • A high osmotic pressure of the cell plays an important role in the protection of the plants against drought and frost injury.
  • Also prevents and controls dehiscence of fruits and sporangia.


i) https://byjus.com/biology/osmosis/

ii) https://www.futurelearn.com/info/courses/teaching-biology-inspiring-students-with-plants-in-science/0/steps/58750

iii) http://www.vivo.colostate.edu/hbooks/pathphys/topics/osmosis.html

iv) https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/05%3A_Structure_and_Function_of_Plasma_Membranes/5.2%3A_Passive_Transport/5.2E%3A_Osmosis

Osmosis: introduction, types and significance