Osmotic pressure in nature and human life

The material provided to your review will provide information on the osmotic pressure (g). Below will be considered: the formulation of the term, features and properties, methods of measuring pressure, the relationship with biology and the relationship with solutions (pp) of different types.

Familiarity with osmotic pressure

Osmotic pressure is the excess hydrostatic pressure exerted on solutions. At the same time, the solutions themselves should be separated by a semi-permeable membrane type from pure solvents. The process of diffusion dissolution through the membrane in such conditions does not occur. The purpose of this pressure is to strive to create an equal balance between the concentrations of any solutions, and the tool is the meeting of molecular diffusion between the solute and solvent. Osmotic pressure is denoted by the letter "π" (pi).

About properties

Osmotic pressure has the tonicity phenomenon, which is a gradient measure of osmotic pressure.In other words, this is the potential of water difference in a pair of p-ditch separated by a semipermeable membrane. Hypertonic solution is a substance that has a higher osmotic pressure in comparison with another p-rum. A hypotonic solution, on the contrary, has a lower osmotic index.

osmotic pressure

If such a solution is placed in a closed space, for example, in a blood cell, then we will see that osmotic pressure can break the cell membrane. The drugs introduced into the blood are first mixed with an isotonic p-rum, bringing them to dissolution precisely because of this reason. At the same time, sodium chloride in the solution should be contained in an amount that can balance the osmotic effect of the cellular fluid.

In case the drugs of the type administered were made on the basis of water or highly diluted solutions, osmotic decomposition would break the blood cells by forcing water to penetrate into them. Creating solutions using too high concentrations of substances will force the water to leave the cells, and as a result they will shrink. For this it is enough from three to ten percent sodium chloride in the p-re.

osmotic pressure law

Plant cells, unlike animals, will be subjected to separation from the cell wall, all its contents, with the exception of the outer cell wall, but together with the membrane. This phenomenon is called plasmolysis. Deplazmolizom, in turn, is the process observed when moving shrunk cells into a solution of a more dilute type.

The relationship of pressure and solution

The chemical nature of the solutes in the compound does not affect the magnitude of the osmotic effect. Its rate depends on the amount of these substances in the p-re. Therefore, we see that osmotic pressure is a colligative property of the solution. The pressure will increase with increasing concentration of active substances in the p-re. This is indicated by the law of osmotic pressure. The formula is quite simple:

π =i·C·R·T,

where the isotonic coefficient is denoted by the letteri, the molar level of concentration of p-ra is expressed byC(mol / m3), the universal gas index of its constant denoted by the letterR,aT- this is the thermodynamic level of the p-ra temperature.

The formula is similar to the ideal gas law. In air, particles of an ideal gas in a viscous-type solvent medium by the similarity of their properties also indicate their common features.This statement confirms a number of experiments conducted by J. B. Perrin in 1906. He observed the process of distribution of emulsion particles of gummigovoy resin in the water column, which generally obeyed the Boltzmann law.

osmotic pressure

There is a concept of oncotic osmotic pressure, which depends on the amount of proteins in the solution. As a result of starvation or kidney disease, the concentration of proteins will decrease. For this reason, oncotic pressure will fall, and edemas of oncotic nature will begin to appear. There will be a transfer of water from the tissues to the vessels, to those places where πHe tomore. Purulent processes cause an increase in πHe totwo to three times. This is due to the destruction of proteins, which leads to an increase in the number of particles.

The stable osmotic index should be approximately 7.7 atm. For this reason, isotonic solutions usually contain about πplasma= 7.7 atm. Solutions with πexceeds πplasma,used to remove pus from wounds or eliminate edema of an allergic nature. And they are also laxative medicines.

Thermodynamic view of osmotic pressure

Vant-Hoff formula used for osmotic treatment can be justified from a thermodynamic point of view.

osmotic pressure law

Free energy, being in solution, will correspondG=G0+RTlnxA+ πVC. The molar part of the solution will be denotedxA,VCIs an indicator of molar volume. Member πVCequivalent to introducing free energy of external pressure. Pure solvent hasG=G0. If the equilibrium index is ∇Gsolvent corresponds to the indicator 0, then we get:

0 = ∇G=G0+RTlnxA+ πVC-G0=RTlnxA+ πVC.

The resulting record can be converted to the formula of van't Hoff.

About colloidal solutions

Osmotic pressure of the solution can occur if two conditions are present:

  1. A semipermeable partition (membrane) is required.
  2. The presence of two solutions on both sides of the membrane, while the solutions must be of different concentrations.

The cell membrane can pass particles of specific sizes, for example, let in and let out a water molecule, but have the opposite effect on C2H6O. Thus, with the help of special materials, which are also characterized by a similar possibility of separation, it is possible to separate the various components of the mixture.

osmotic pressure of the solution

Osmotic solutions are calculated using π = cRT. This formula was derived by Vant-Hoff in 1885, and the basis for finding it was Pfeffer's experiments with porous porcelain.

Turgor in a cage

Both osmosis and osmosis are very important components of many biological systems. If the structure contains a semipermeable septum (a specific tissue or cell wall), then a constant water osmosis rate will create too much hydrostatic pressure, and as a result, a turgor will form, which will provide the strength and resilience of the tissues.

Perhaps the phenomenon of hemolysis, which is a rupture of the cell membrane, such as the erythrocyte as a result of its excessive swelling when placed in purified water.

osmotic pressure of the solution


Opposite processes will occur when the cell is placed in solutions of a salt of a concentrated type: water contained in the cell will diffuse into the salt solutions through the membrane. As a result, the cell will shrink, losing its turgor of a stable state. This phenomenon is called plasmolysis.However, turgor can be restored by placing a plasmolyzed cell in protoplasmic water. Cell volume will be maintained only in an isotonic p-re with the same concentration (constant osmotic).

Summing up

This material allowed the reader to get acquainted with the concept of osmotic treatment, formulate a general idea about it and learn a lot of interesting things. For example, the similarity of the calculation of the formula with the Van't Hoff formula, the similarity with the ideal gas, the role in biological processes and the consequences that they can cause, namely, turgor, plasmolysis, hemolysis and much more.

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