1 June 2023

Osmosis is a naturally occurring phenomenon in most living beings and in some industrial processes. Although osmosis seems to be a simple process, its understanding is fundamental in fields such as biology, chemistry and engineering, since it plays a key role in the functioning of cells, tissues, organs and systems.

In addition, it has important practical implications in our daily lives. In this article we will explore the basics of osmosisits applications and how we can better understand this very interesting process.

Definition and concept of osmosis

It is a physical-chemical process in which a solvent, generally water, moves through a semipermeable membrane or plasma membrane from a solution of lower solute concentration to one of higher solute concentration. This membrane allows the passage of the solvent, but not of the solutes, which results in an equilibrium of concentrations on both sides of it.

The semipermeable membrane allows the passage of water molecules, but does not allow the passage of other larger molecules or ions, therefore it is a selective process that depends on the difference in concentration between the two solutions and the permeability of the membrane.

Osmosis is an essential process in biology, since allows nutrient absorption and elimination of waste in cells. It also has important applications in industry, agriculture, and medicine, such as in water purification and in monitoring blood pressure in patients with kidney failure.

What is the osmosis process?

In osmosis, the solvent moves from the more dilute solution to the more concentrated solution, through the semipermeable membrane. This occurs because the solvent molecules move in the direction of the more concentrated solution to dilute it and reach equilibrium. This process continues until the concentrations of the solutions are equal on both sides of the membrane.

It is very important in cell biology, where cells must maintain an osmotic balance to survive. For example, if a cell is placed in a hypertonic solution (more concentrated than the fluid inside the cell), the water will move out of the cell by osmosis, which can cause the cell to dehydrate and die. On the other hand, if it is placed in a hypotonic solution (less concentrated than the fluid inside the cell), the water will move into the cell, which can cause the cell to swell and rupture.

What is osmosis used for?

It is a process fundamental in the field of biology and chemistry that allows the movement of water through semipermeable membranes from a solution of lower solute concentration to a solution of higher solute concentration.

osmosis has numerous practical applications in everyday life and in industry. Some examples include:

  1. Regulation of osmotic pressure in living cells: In the case of physiology, it plays an important role in regulating fluid balance in the body. It is important for maintain homeostasis in cells of our body, since it allows the entry and exit of water or solutes necessary for its normal functioning. It is also important in the environment for the same reason, for example, plants use osmosis to absorb water and nutrients from the soil through their roots.
  2. Water purification: Reverse osmosis is a process used to remove impurities of the water by applying a pressure that forces water to pass through a semi-permeable membrane, leaving impurities behind.
  3. The ultra fixation: This allows the solution to be concentrated on the side of high solute concentration. This technique is used in many manufacturing processes. purification and concentration of solutionssuch as in the production of drinking water from salt water or in the concentration of proteins in the food industry.
  4. Food preservation: Osmosis dehydration is a technique used to preserve food, in which the food is immersed in a concentrated solution of salt or sugar to extract the water and thus prolong its useful life.
  5. Energy production: It can be used to generate power by using a semi-permeable membrane to separate two solutions of different concentration, creating a pressure difference that can be used to generate electrical energy.

What are the types of osmosis?

There are several types of osmosis that They are classified according to environmental conditions. where diffusion of water occurs.

Each has unique implications for biological and chemical processes, and understanding the differences between them is important to understand how osmosis works in different contexts. The three types most important are:

  • isotonic: The concentration of solutes inside the cell is the same as outside it. It is important in cell biology and physiology as it allows cells to maintain their proper form and function in an environment with a constant solute concentration.
  • hypertonic: Water will move from the cell with a lower concentration of solutes to the outside of the cell, which can cause the cell to shrink or dehydrate. This can be beneficial for the body or have negative effects, and it can also be useful in preserving food.
  • hypotonic: Water moves from the less concentrated solution to the interior of the cell where it is more concentrated, this to balance the concentration of solutes on both sides of the membrane. Is important in many biological processes, such as the absorption of water by the cells of organisms and the generation of turgor pressure in plant cells. Excess hypotonic osmosis can cause cells to lyse or rupture.

Inverse osmosis

It is used as a Water purification process in which it is forced to pass through a semi-permeable membrane to separate the contaminants and impurities it contains. To do it, the water is subjected to high pressure and forced to pass through that membrane, which allows only pure water to pass through it, thereby retaining contaminants and the impurities.

This process is very effective in removing impurities such as chlorine, sediment, dissolved minerals and organic chemicals. It is also widely used in the purification of drinking water, the production of demineralized water for industry, and in the production of water for use in industrial processes.

It is important to note that it requires a lots of power to run and can generate large amounts of wastewater. Additionally, the semi-permeable membrane used in the process may require periodic maintenance and replacement.

direct osmosis

It corresponds to a process where a concentrated solution is applied to one side of the semipermeable membrane and the pure solvent flows through this toward the dilute side, creating a permeate stream.

Unlike reverse osmosis, which uses pressure to force water through a semi-permeable membrane, direct osmosis uses a concentrated solution to generate pressure osmotics necessary for the process. This process is commonly used in the food and beverage industry for the concentration of juices, as well as being useful for the desalination of seawater.

Another point to highlight is its medical and pharmaceutical applications, where it is used for protein purification and drug concentration. In addition, it can be used in wastewater treatment and energy production, as an alternative to reverse osmosis or distillation.

How does the osmosis process work?

The semipermeable membrane is selective in terms of the types of molecules it allows to pass through it. In the case of osmosis, the membrane allows the passage of water moleculesbut does not allow larger or charged solute molecules to pass through.

When two solutions with different concentrations of solutes are separated by a plasma membrane, water molecules will move from the solution with low concentration of solutes to the solution with high concentration of solutes. This movement is due to natural tendency of water molecules to diffuse through a membrane to equalize the concentration on both sides of the membrane.

This process has important implications in biology and in other fields of science, since the cell, for example, is surrounded by a plasma membrane and osmosis is beneficial for maintaining the cell homeostasis. In addition, it is responsible for regulating the concentration of solutes inside and outside the cell.

Therefore, dissolution is essential for osmosis, since it affects the concentration of solutes and therefore the osmotic pressure, which in turn determines the direction and speed of the flow of water through the semipermeable membrane.

What are the stages of osmosis?

The stages of osmosis are the following:

  1. Diffusion: In the first stage, the solvent (water) molecules move through the semipermeable membrane from the less concentrated solution to the more concentrated solution, down the concentration gradient.
  2. Osmotic pressure: As the water molecules move toward the more concentrated solution, they exert pressure on the semipermeable membrane. This pressure is known as osmotic pressure.
  3. Balance: As diffusion continues, the osmotic pressure increases in the more concentrated solution and decreases in the less concentrated solution, until the two solutions reach a osmotic balance in which the osmotic pressure is equalized on both sides of the semipermeable membrane.

It is important to note that this process occurs constantly and continuously until osmotic equilibrium is reached.

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