Osmosis

Osmosis Definition

“Osmosis is a process by which the molecules of a solvent pass from a solution of low concentration to a solution of high concentration through a semi-permeable membrane.” 

Osmosis

Table of Contents

• Explanation
• Solutions
• Types
• Effects
• Osmotic Pressure
• Significance
• Examples

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.

Any solvent can undergo the process of osmosis including gases and supercritical liquids.

Let us have a detailed look at the different types and effects of osmosis in detail.

Also Refer: Difference between osmosis and diffusion

There are three different types of solutions:

• Isotonic Solution

• Hypertonic Solution

• Hypotonic Solution

An isotonic solution is one that has the same concentration of solutes both inside and outside the cell.

A hypertonic solution is one that has a higher solute concentration outside the cell than inside.

A hypotonic solution is one that has a higher solute concentration inside the cell than outside.

Osmosis is of two types:

• 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.

Also Read: Difference between endosmosis and exosmosis

Osmosis affects the cells differently. An animal cell will lyse when placed in a hypotonic solution compared to a plant cell. The plant cell has thick walls and requires more water. The cells will not burst when placed in a hypotonic solution. In fact, a hypotonic solution is ideal for a plant cell.

An animal cell survives only in an isotonic solution. In an isotonic solution, the plant cells are no longer turgid and the leaves of the plant droop.

The osmotic flow can be stopped or reversed, also called reverse osmosis, by exerting an external pressure to the sides of the solute. The minimum pressure required to stop the solvent transfer is called the osmotic pressure.

Osmotic pressure is the pressure required to stop water from diffusing through a membrane by osmosis. It is determined by the concentration of the solute. Water diffuses into the area of higher concentration from the area of lower concentration. When the concentration of the substances in the two areas in contact is different, the substances will diffuse until the concentration is uniform throughout.

Osmotic pressure can be calculated using the equation:

Π=MRT

where Π denotes the osmotic pressure,

M is the molar concentration of the solute,

R is the gas constant,

T is the temperature

• Osmosis influences the transport of nutrients and the release of metabolic waste products.

• It is responsible for the absorption of water from the soil and conducting it to the upper parts of the plant through the xylem.

• It stabilizes the internal environment of a living organism by maintaining the balance between water and intercellular fluid levels.

• It 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.

Also Refer: Passive Transport

Osmosis has a significant role to play in plants, animals and also in humans. In an animal cell, osmosis helps in absorbing water from the intestines to the blood.

Listed below are more examples of Osmosis.

• The absorption of water from the soil is due to osmosis. The plant roots have a higher concentration than the soil. Therefore, the water flows into the roots.

• The guard cells of the plants are also affected by osmosis. When the plant cells are filled with water, the guard cells swell up, and the stomata open.

• If a freshwater or saltwater fish is placed in the water with different salt concentrations, the fish dies due to the entry or exit of water in the cells of the fish.

• Humans suffering from cholera are also affected by osmosis. The bacteria that overpopulate the intestines reverse the flow of absorption and do not allow water to be absorbed by the intestines, which results in dehydration.

• When the fingers are placed in water for a longer period of time, they become pruney due to the flow of water inside the cells.

Also Read: Reverse Osmosis

For more information on osmosis, its definition, types, effects and osmotic pressure, keep visiting BYJU’S Biology website or download the BYJU’S app for further reference.