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Osmosis


Osmosis is the movement of solvent molecules from a dilute solution to a concentrated solution (or from a pure solvent into its solution) across a semi-permeable membrane.

Imbibition is the phenomenon by which living or dead cells absorb water by surface attraction.
Example: Wooden Doors get swollen during the rainy season.
Dry seeds swell up when placed in a can of water.

Diffusion is movement of molecules of liquids and gases from their region of higher concentration to their region of lower concentration until it is same throughout the given space.
Example: When perfume is spilt in one corner of a room its fragnance spreads all over the room.

Osmotic Pressure is the pressure exerted by the liquid column that just prevents the entry of solvent particles into the solution across a perfectly semi-permeable membrane.

Osmotic Potential of a solution is the tendency of water molecules to diffuse out of it.It is a measure of the difference in the concentration of the solution with water.

Isotonic Solutions : Two solutions having the same osmotic pressure(same concentrations) at the same temperature are said to be isotonic.

Hypertonic Solution : The solution having the higher concentration of solute molecules (higher osmotic pressure) when compared to another solution is said to be hypertonic.

Hypotonic Solution : The solution having the lower concentration of solute molecules (lower osmotic pressure) when compared to another solution is said to be hypotonic.

Endosmosis : The inward movement of solvent molecules through the semi permeable membrane by the process of osmosis is called endosmosis.

Exosmosis : The outward movement of solvent molecules through the semi permeable membrane by the process of osmosis is called exosmosis.

Turgidity : A cell charged with water with its wall in a state of tension is said to be turgid and the condtion is described as turgidity.

Flaccidity : A cell no longer charged with water is said to be flaccid and the condition is described as flaccidity.

Turgor Pressure : The outward pressure exerted by the liquid contents of the cell on the cell wall under fully turgid condition.

Wall Pressure : The inward pressure exerted by the cell wall on the liquid contents of the cell under fully turgid condition.

Suction Pressure : It is a measure of the water absorbing power of a cell. It is the difference between the Osmotic Pressure and the Turgor Pressure.

Plasmolysis : The shrinkage of the protoplasmic contents away form the cell wall when the cell is placed in a hypertonic solution.

Deplasmolysis : The return of a plasmolysed cell to its normal condition when placed in a hypotonic solution.

Ascent of Sap : The upward movement of water and dissolved minerals from the root to the top of tall trees through the xylem vessels.

Root Pressure : It is the pressure exerted by the cortical cells of the root upon their fluid contents under fully turgid condition ; forcing a quantity of them into the xylem vessels and upwards into the stem.

Capillarity : It is the phenomenon by which liquids rise to the greatest height in tubes having the narrowest bore(diameter).

Significance Of Osmosis

In Plants :
1.Absorbption of water from the soil.
2.Opening and closing of stomata.

In Animals :
1.Fresh water animals have to maintain their osmotic pressure with the external environment. Thus they are either having a contractile vacuole (as in amoeba) which discharges the waste materials or kidneys (like in fish and frog).
2.In land animals kidneys regulate the osmotic pressure of the blood.

Marine fishes being in a hypertonic medium tend to accumulate salts in their body .Thus when they are placed in tap water their cells 'burst' due to absorbing excess water.

Differences between Osmosis and Diffusion

Osmosis
1.
It involves flow of solvent molecules in one direction.
2.It requires semi permeable membrane.
3.It is a slow process .
4.Occurs only in liquids.
5.The movement is over a short distance.

Diffusion
1
.Flow of either solute or solvent molecules is in both directions.
2.No such membrane is required.

3.It is a fast process.
4.Occurs in liquids as well as gases.
5.Movements are over large distances.

In the case that you have a doubt on a something listed here or want to know something that has not been mentioned please use our Reference Boards .


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