Meaning of Osmosis

What is Osmosis:

Osmosis is the movement of a solvent through a semi-permeable membrane between two solutions with different concentrations. It is a physical phenomenon that is generated spontaneously and without energy expenditure.

In turn, osmosis is a process of vital importance for the survival of cells and the cellular metabolism of living beings, hence it is also part of the studies of biology.

The word osmosis derives from the Greek osmos, which means 'impulse'.

Osmosis occurs when there are two solutions that have different concentrations. In this case, when the water or solvent moves through the semipermeable membrane, it does so in order to balance both concentrations.

In this process, the solvent or substance to be dissolved tends to cross the semi-permeable membrane, which has pores of molecular dimension that do not allow the passage of solute molecules, but of the solvent.

In this way, the solution with the lowest concentration increases the amount of that element and in the other it decreases until it becomes equal. This effect continues until hydrostatic pressure balances this trend.

We speak of active transport when the cell has an energy expenditure and passive transport when the energy expenditure is not necessary.

Osmosis can be carried out in different types of solution in which a particular osmotic pressure is applied as required. They are identified below:

  • Hypotonic solution: it is the one in which there is a lower concentration of solute depending on the environment in which it is found.
  • Hypertonic solution: the solute concentration is higher depending on the environment in which it is found.
  • Isotonic solution: it is one that has the same concentration of solute and solvent.

See also Solute and solvent.

Osmosis in plant and animal cells

Osmosis is also a process used in the exchange processes in the nutrition of animal and plant cells.

In the plant cell, osmosis involves a combination of diffusion through the membrane bilayer and mass flow through the pores of the membrane, these pores are formed by aquaporins that form selective water channels.

On the other hand, in the animal cell, osmosis is the phenomenon in which the transport of water occurs through the plasma membrane with the reinforcement of the phospholipid bilayer.

There are diseases that are associated with problems in the osmosis of the cell that shows symptoms such as:

  • Dehydration, loss of water and mineral salts from a body.
  • Oxygen transport deficiency.
  • Polyuria, manifestation of a higher volume of urine than expected.
  • Polydipsia, abnormal increase in thirst.

Inverse osmosis

Reverse osmosis is the opposite process, in which the substance (solute) is separated from the solvent by applying a surface pressure greater than the osmotic pressure on the impermeable membranes that do not allow water to pass through, thus opposing the normal flow of osmosis.

This process can be applied in various situations such as, to remove alcohol from beer or to concentrate whey, for example from cheese and many other industrial processes.

Osmosis and diffusion

Osmosis and diffusion are two types of passive transport that occur between two solutions in order to equalize their concentrations.

Diffusion is the transport of solutes through membranes, from the more concentrated medium (hypertonic) to the less concentrated medium (hypotonic).

Osmosis is the passage of the substance to dissolve, from the medium of higher concentration to the medium of lower concentration.

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