Osmosis: Definition, Mechanism, and Examples

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What is Osmosis?

The net flow of solvent molecules through a semipermeable membrane is referred to as osmosis. It’s comparable to diffusion in that it moves downhill, from a higher to a lower concentration. However, in osmosis, the movement must take place over a semipermeable barrier. 

Osmosis, Osmosis Definition, What is Osmosis, Osmosis Examples,

Osmosis cannot be called osmosis without this component. While diffusion refers to the net movement of solutes between two solutions, osmosis is concerned with the net movement of solvent molecules, such as water molecules. The difference in water molecule concentration between the two sides of the membrane is what causes the water to migrate in order to bring the concentrations of the two sections closer together.

Osmosis Definition

Osmosis is defined in biology as the net transfer of water molecules from a higher to a lower water potential area through a semipermeable membrane (e.g., the cell membrane).

Other osmosis definitions are as follows:

1. The process of a solvent diffusing from a low-solute-concentration area to a high-solute-concentration area via a semipermeable barrier.

2. The ability of water to flow through a semipermeable barrier from a hypotonic solution (low concentration of dissolved chemicals) to a hypertonic solution (high concentration of dissolved substances).

Osmosis is characterized similarly in chemistry. When two solutions are separated by a membrane that selectively inhibits the passage of solute molecules while allowing the passage of solvent molecules. It is the passage of a pure solvent from one with a lower concentration of solutes to another with a higher concentration of solutes.

Osmosis Etymology

The word osmosis is a Latinized version of the now-defunct osmose. Osmotic is a derived word that means “pertaining to or of the character of osmosis.” Osmotic pressure, for example, is a pressure that occurs as a result of osmosis.

How Osmosis Works?

(1) net downhill flow of water molecules, (2) a selectively permeable membrane, and (3) an osmotic gradient are all required for osmosis to occur. Water molecules tend to migrate downhill, from a high-water concentration (or fewer solutes) to a low water concentration (or vice versa) (or greater solutes).

It cannot be considered osmosis if there is no net flow of water. It should also include a semipermeable barrier to allow for movement. Without it, the process is only diffusion rather than osmosis. Because water molecules are polar, channel proteins are required for them to travel along their concentration gradient.

These channel proteins are implanted in the cell membrane and create a hydrophilic conduit for water to flow through. The osmotic (pressure) gradient, or the difference in osmotic pressures between the two solutions, is what causes the water molecules to migrate.

Water potential is a measurement of the relative tendency of water to migrate from one location to another. The Greek letter Ψ is often used to symbolise it (Psi). Different tonicities of solutions produce a net flow of water across the cell membrane.

A solution consists mostly of the solute (material to be dissolved) and the solvent (the component that dissolves the solutes). The concentrations of components in two solutions will decide whether one is isotonic, hypotonic, or hypertonic in comparison to another.

Isotonic Solution

An isotonic solution is one in which the number of solutes in one solution is about equal to the number of solutes in another solution. A cell that is isotonic to the outside solution, for example, indicates that the internal fluid and the outside fluid have the same osmotic pressure and water potential. There will be no net flow of water molecules between the cell and the surrounding fluid in this instance.

Hypotonic Solution

A hypotonic solution is one that has a lower osmotic pressure (or contains fewer solutes) than the solution it is compared to. To dilute the solution, water flows toward the area with less water concentration or towards the more concentrated portion. Water will flow across the membrane and into the cell’s more concentrated solution if the fluid around the cell is hypotonic, for example.

Hypertonic Solution

A hypertonic solution is one that appears to be the polar opposite of a hypotonic solution. In comparison to the other solutions, a hypertonic solution contains more solutes and less water. Water will exit a cell submerged in a hypertonic solution to dilute the solution outside.

Osmosis Examples

i. Osmosis in Animal Cells

Osmosis is important in biological systems because many biological membranes are semipermeable, and it has a variety of physiological consequences. When animal cells are exposed to a hypertonic (lower water concentration) environment, the water leaves the cells, causing the cells to shrink. Crenation is the medical term for this ailment. When animal cells are put in a hypotonic environment (i.e., one with greater water content), water molecules migrate into the cells, causing them to expand. Cells will eventually rupture if osmosis persists and becomes extreme.

ii. Osmosis in Plant Cells

Plant cells do not rupture owing to an excessive amount of water input. Plants use their cell walls and vacuoles to protect themselves against excessive osmosis. The plant cell is stabilised by osmotic pressure exerted by the cell wall. Osmotic pressure, in fact, is what keeps plants upright. The big vacuole inside the plant cell aids osmoregulation, a regulatory process in which water potential is controlled to keep the osmotic pressure inside the cell within the optimal range.

Water efflux, on the other hand, does not protect plant cells. When a plant cell is put in a hypertonic environment, the cell wall is unable to prevent water loss. Cells shrink or become flaccid as a result of this.

Osmosis Citations


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