Diffusion and osmosis

The diffusion and osmosis are characterized by the distribution of phenomena molecules of a body in another body that is in contact with the first or separately, but through a membrane semiplasmática. These two possibilities are precisely what opens the division between the two processes.

What is diffusion?

It is the diffusion that produces an intermingling of the molecules, as a consequence of a movement that drives their kinetic energy. The bodies are in contact so the molecules are distributed, in a phenomenon explained by the kinetic theory of matter.

This movement occurs in any of the states of matter, but it is more easily observed in the case of liquids. The tendency of movement is towards the formation of a uniform mixture of the two types of molecules.

The scientist Adolf Fick established in 1855 some laws that bear his name and describe various cases of the diffusion of matter in a medium in which initially there is no equilibrium. These laws relate the density of the flux of the molecules to the concentration difference between the two media separated by the membrane, the diffusion coefficient of the same, and the permeability of the membrane.

Some cases of cell diffusion will be exemplified below.

Examples of diffusion

  1. The passage of oxygen in the pulmonary alveoli.
  2. Nerve impulses, which involve sodium and potassium ions through the axon membrane.
  3. If you take a diffuser pair consisting of two metals brought into contact through their faces and bring the temperature below the melting point, you will see that the composition has changed: the nickel atoms have melted towards the copper.
  4. The warming and color change of a cup of coffee when a good proportion of cold milk is added.
  5. The entry of glucose into the red blood cells from the intestine.
  6. In an estuary, less dense river water diffusion occurs than flows over seawater.
  7. If you put a tablespoon of sugar in a glass of water, the sucrose molecules diffuse through the water.
  8. The diffusion of gases can be seen when a perfumed person enters a closed place, and everyone immediately feels the smell. The same thing happens when someone smokes indoors.

What is osmosis?

The main characteristic of the semipermeable membrane that gives rise to the osmosis process is that it allows the passage of the solvent, but not the solute, as it contains pores of the molecular size that assign these characteristics.

In this way, it is observed that the solvent tends to cross the membrane in the direction of the solution whose concentration is higher, which ends up producing that the number of solvent increases in the most concentrated part and decreases in the least concentrated part. It is a process that is repeated until the hydrostatic pressure balances the trend.

Because it is important?

The solubility of the solute in the solvent and the nature of the membrane to use the fundamental factors that determine the effectiveness of the osmotic process: the so-called ‘solubility’ is determined by the chemical bonds that each component in the solution presents.

The osmotic process is fundamental in biological processes where water is the solvent, especially in those processes intended to maintain the water and electrolyte balance in living beings, regulating water levels in the cell or in the body in general: Without this process, there could be no fluid regulation and nutrient absorption.

Examples of the osmosis

  1. Single-celled living things that live in freshwater enter large amounts of water through osmosis.
  2. The absorption of water by the roots in plant organisms, which allows growth, occurs through such a phenomenon.
  3. Obtaining water from epithelial cells by the large intestine is such a process.
  4. A common osmosis experiment consists of breaking a potato, placing a little sugar with water on one end, and a plate with water on the other. The potato acts as a membrane, and after a while, it will be seen that the solution that had sugar now has more liquid.
  5. The ADH hormone that allows the reabsorption of water by the collecting tubule in the kidneys.
  6. The elimination of the very dilute urine by which the fish expel the maximum liquid with the minimum loss of salts.
  7. The elimination of water through sweat in people is done through osmosis.
  8. Filters to purify water work with osmosis since they are made with a material that allows water to pass through, but not larger molecules.


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