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?
Diffusion produces an intermingling of the molecules, as a consequence of a movement that drives its kinetic energy . The bodies are in contact then 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 is more easily observed in the case of liquids . The tendency of the 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 there is initially no equilibrium. These laws relate the density of the flow of the molecules with the difference in concentration between the two media separated by the membrane, the diffusion coefficient of the same and the permeability of the membrane.
Next, some cases of cell diffusion will be exemplified.
- The passage of oxygen in the pulmonary alveoli.
- Nervous impulses, which involve sodium and potassium ions through the axon membrane.
- If a diffusing pair formed by two metals put in contact through their faces is taken, and the temperature is brought below the melting point, it will be verified that the composition has changed: the nickel atoms have melted towards the copper.
- The warm and color change of a cup of coffee when you add a good proportion of cold milk.
- The entrance of glucose to the red blood cells, coming from the intestine.
- In an estuary, there is a diffusion of the less dense river water that flows over the seawater.
- If a spoonful of sugar is placed in a glass of water, the sucrose molecules diffuse through the water.
- The diffusion of the gases can be seen when a perfumed person enters a closed place, and everyone immediately feels the smell. The same happens when someone smokes in a closed place.
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 of the solute : it contains pores of 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 the amount of solvent in the most concentrated part and decreasing in the less 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 aimed at maintaining 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 regulation of liquids and absorption of nutrients .
Examples of the osmosis process
- Unicellular living beings that live in fresh water enter large amounts of water through osmosis.
- The absorption of water by the roots in plant organisms, which allows growth, occurs through a phenomenon of this type.
- Obtaining water from the epithelial cells, by the large intestine, is a process of this type.
- A common experiment of osmosis is to split a potato, placing at one end a bit of sugar with water, and on the other a dish with water. The potato acts as a membrane, and after a while it will be seen that the solution that had sugar now has more liquid.
- The ADH hormone that allows the reabsorption of water by the collecting tubule, in the kidneys.
- The elimination of very diluted urine by which the fish expel the maximum liquid with the minimum loss of salts.
- The elimination of water through sweat in people is done through osmosis.
- The filters to purify the water work with osmosis, since they are made with a material that allows the passage of water, but not larger molecules.