Osmotic pressure is a colligative propertymeaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity. Osmosis is a vital process in biological systemsas biological membranes are semipermeable.
In general, these membranes are impermeable to large and polar molecules, such as ionsproteinsand polysaccharideswhile being permeable to non-polar or hydrophobic molecules like lipids as well as to small molecules like oxygen, carbon dioxide, nitrogen, and nitric oxide.
Permeability depends on solubility, charge, or chemistry, as well as solute size. Water molecules travel through the plasma membrane, tonoplast membrane vacuole or organelle membranes by diffusing across the phospholipid bilayer via aquaporins small transmembrane proteins similar to those responsible for facilitated diffusion and ion channels.
Osmosis provides the primary means by which water is transported into and out of cells. The turgor pressure of a cell is largely maintained by osmosis across the Vattenrelaterat membrane between the cell interior and its relatively hypotonic environment.
Some kinds of osmotic flow have been observed since ancient times, e. Osmosis is the movement of a solvent across a semipermeable membrane toward a higher concentration of solute. In biological systems, the solvent is typically water, but osmosis can occur in other liquids, supercritical liquids, and even gases.
When a cell is submerged in waterthe water molecules pass through the cell membrane from an area of low solute concentration to high solute concentration. For example, if the cell is submerged in saltwater, water molecules move out of the cell. If a cell is submerged in freshwater, water molecules move into the cell.
When the membrane has a volume of pure water on both sides, water molecules pass in and out in each direction at exactly the same rate. There is no net flow of water through the membrane. Osmosis can be demonstrated when potato slices are added to a high salt solution.
The water from inside the potato moves out to the solution, causing the potato to shrink and to lose its 'turgor pressure'. The more concentrated the salt solution, the bigger the loss in size and weight of the potato slice. Chemical gardens demonstrate the effect of osmosis in inorganic chemistry.
The mechanism responsible for driving osmosis has commonly been represented in biology and chemistry texts as either the dilution of water by solute resulting in lower concentration of water on the higher solute concentration side of the membrane and therefore a diffusion of water along a concentration gradient or by a solute's attraction to water resulting in less free water on the higher solute concentration Vattenrelaterat of the membrane and therefore net movement of water toward the solute.
Both of these notions have been conclusively refuted. The diffusion model of osmosis is rendered untenable by the fact that osmosis can drive water across a membrane toward a higher concentration of water. It is difficult to describe osmosis without a mechanical or thermodynamic explanation, but essentially there is an interaction between the solute and water that counteracts the pressure that otherwise free solute molecules Vattenrelaterat exert.
One fact to take note of is that heat from the surroundings is able to be converted into mechanical energy water rising. Many thermodynamic explanations go into the concept of chemical potential and how the function of the water on the förändra osmosik side differs from that of pure water due to the higher pressure and the presence of the solute counteracting such that the chemical potential remains unchanged.
The virial theorem demonstrates that attraction between the molecules water and solute reduces the pressure, and thus the pressure exerted by water molecules on each other in solution is less than in pure water, allowing pure water to "force" the solution until the pressure reaches equilibrium.
Osmotic pressure is the main agent of support in many plants.