Biology

Osmosis

Osmosis is the spontaneous movement or diffusion of water molecules from a region of higher concentration to a lower concentration through the semi-permeable membrane. However, osmosis can occur in other liquids too. A semi-permeable membrane is a membrane that allows certain particles according to their size to pass through them. For example, cell membrane. Let’s study it in detail here.

Osmosis

Osmosis Definition

This process was firstly introduced by German physiologist; Wilhelm Pfeffer however the term osmose (osmosis) was given by Thomas Graham in 1854. It is a passive movement which means that it takes place without using any cell energy. Therefore, it is a spontaneous process.

Solutions

However, there are only three types of osmotic solutions. These are as follows:

1. Hypotonic Solution

In hypotonic solutions, the concentration inside the cell is lower than the concentration outside the cell. Meanwhile, due to lesser concentration, the liquid outside the cell comes inside causing the cell to swell up. For example- Distilled water.

2. Hypertonic Solution

In hypertonic solutions, the concentration inside the cell is however higher than the concentration outside. As a result, the contents inside the cell move outside causing the cell to shrink. For example- Seawater, sugar drinks.

3. Isotonic Solution

In an isotonic solution, both the cell solution and the medium solution have the same concentration. This way there is no flow of liquid and the solution remains the same. In other words, there is neither the shrinkage nor expansion of the cells. For example- blood Most importantly, for hypertonic and hypotonic solutions there must be a solution for comparison.

Factors Affecting Osmosis

Osmotic Pressure

The pressure between two different solutions is necessary for the phenomenon to occur. Water moves from the area of higher to lower concentration. Therefore, a gap in concentration is a must. When the concentration of both the solutions becomes equal the phenomenon stops.

Moreover, osmotic pressure is a colligative property. This means that the osmotic pressure only depends upon the concentration of solute and not its chemical properties.

Osmotic Gradient

The osmotic gradient is the difference in the concentration of both solutions. However, osmosis is inversely proportional to the concentration gradient. When both the solutions reach equilibrium, the diffusion stops. In other words, when the concentration of both the solutions becomes the same, the flow stops.

Types

Endosmosis

In endosmosis, we keep the cell in the hypotonic solution. As a result, the solvent moves inside the cell causing the cell to turgid (full) or swell up.

Exosmosis

In exosmosis, we keep the cell in the hypertonic solution. As a result, the cell sap moves out making the cell flaccid (loose).

Importance

It has great importance in both human and plant life. Moreover, in research fields, it also possesses great importance. Some of them are as follows-

  • It is the main factor for the absorption of water and from the soil in plants. Moreover, the conduction of water is also its task.
  • Helps in maintaining turgidity in the cells, therefore, maintaining mechanical support.
  • Maintains water and fluid balance in living beings.
  • Aids in the dehiscence of fruits and sporangia.
  • Helps the plant from injury because of droughts.
  • It helps in the absorption of water from the intestines to the blood in animals.

Reverse Osmosis Definition

RO is a process of water purifying. In this process, the solute is made to pass through the semi-permeable with hydraulic pressure. This makes the pure solvent pass on the other side leaving the solute on another.

In other words, this process involves the separation of unwanted or harmful molecules from the water, making it pure.

Advantages of RO

  • It is a great and successful method for softening water.
  • Unwanted ions or big particles can’t enter through a semi-permeable membrane
  • Not much maintenance is necessary.
  • It is environmentally friendly and completely safe.
  • It acts as a better alternative for bottled water.

Disadvantages of RO

  • Too much wastage of water.
  • Disposable wastewater requires great attention.
  • For the deionization, much pressure is in need.
  • The water of RO lacks minerals required for the body
  • Much energy is the need of the process.

Forward Osmosis

This process involves water flow through the semi-permeable membrane by the natural pressure. It is used for various industrial processes.

The uses of FO are-

1. Concentration of Product

The process can draw out excess water from liquid products. As a result, you can get the perfect concentration as per the requirement. This can be applicable to coffee, or beers. The water can be drawn out as a result the shipping can become more reliable. However, it does not alter any natural characters of the products. Therefore, it becomes more reliable.

2. Extraction of Water

This can be useful for the extraction of water for reuse. The quality of water varies. For instance, this water can be useful for irrigation, washing, cooling machines, and sometimes even for drinking.

3. Wastewater Concentration

It is useful in many industrial fields. Water is drawn out from the stream by the means of this process. The waste products left behind are easy to dispose of. The water is now reusable for many purposes.

Diffusion vs. Osmosis

Similarities

  • Both are passive processes. That is to say, they do not require any extra energy.
  • The aim of both of them is to reach the equilibrium point. In other words, to make the concentration equal on either side.
  • Moreover, in both of them, the particles move from higher concentration to lower concentration.

Differences

  • Diffusion can occur in any state of matter; solid, liquid, or gas.
  • The semi-permeable membrane is not necessary for diffusion unlike that of osmosis, which certainly requires the membrane.
  • In diffusion both solute, as well as solvent particles can cross the membrane. However, it is not the same for others where only solvent molecules flow.
  • The flow of particles in diffusion occurs in all directions which are not for the other case.

FAQs on Osmosis

Question 1- What is the definition of osmosis in biology? Give an example.

Answer 1- It is the movement of water molecules from the region of higher concentration to the lower concentration through a semi-permeable membrane.

Moreover, this process was firstly introduced by German physiologist; Wilhelm Pfeffer however the term osmose (osmosis) was given by Thomas Graham in 1854. For example -Conduction of water molecules from the soil to the plant tissues.

Question 2- What are the functions of osmosis?

Answer 2- Some of the functions are as follows-

  • It is the main factor for the absorption of water and from the soil in plants. Moreover, the conduction of water is also its task.
  • Helps in maintaining turgidity in the cells, therefore, maintaining mechanical support.
  • Maintains water and fluid balance in living beings.
  • Helps in the absorption of water from the intestines to the blood in animals.

Question 3- Define RO and its advantages?

Answer 3- RO is a process of water purifying. In this process, the solute is made to pass through the semi-permeable with hydraulic pressure. This makes the pure solvent pass on the other side leaving the solute on another.

In other words, this process involves the separation of unwanted or harmful molecules from the water, making it pure.

Advantages of RO

  • It is a great and successful method for softening water.
  • Not much maintenance is necessary.
  • It is environmentally friendly and completely safe.
  • It acts as a better alternative for bottled water.
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