Difference Between Osmosis and Diffusion

The fundamental difference between the two is – Osmosis is the movement of the solvent (water) from a region of higher concentrations to the region of lower concentration through a semipermeable membrane, to maintain the equilibrium. On the other hand, diffusion can be described as the movement of the molecules (solid, liquid or gases) from the region of higher concentration to the region of lower concentrations, but not through a semipermeable membrane.

Both of this kind are the examples of Passive transportation. It is the natural process occurring inside the body and thus promotes the movement of the molecules without a requirement of the energy. The motion can be either through higher to the lower concentration or from lower to the higher concentration, and this difference in concentration of the particles is called concentration gradient.

This process is performed to equalize the concentrations gradient on both the side of membrane especially in a case of water (solvent). In the following content, we will be considering the key differences between both kinds of motion, followed by a brief discussion.

Content: Osmosis Vs Diffusion

1. Comparison Chart
2. Definition
3. Key Differences
4. Conclusion

Comparison Chart

Basis for Comparison	Osmosis	Diffusion
Meaning	The movement of liquid (solvent) especially water from the higher region concentration to the region of lower concentration, through the semipermeable membrane is called osmosis.	The movement of molecules (solid, liquid or gases) from a region of higher concentration to the lower region concentration, but not necessarily through a semi-permeable membrane is called diffusion.
Semi-permeable membrane	The motion is through the semi-permeable membrane.	The motion is direct and does not require the semi-permeable membrane.
Medium	This process undertakes in the liquid medium.	This process undertakes in any medium (solid, liquid and gases).
Type of diffusing molecule	The movement is basically of solvent (water).	The movement can be in solid, liquid, or gases.
Rate of process	Osmosis is a slow process.	Diffusion is the fast process.
Free-energy	Osmosis is dependent on one solvent to the another for the reduction of free energy.	It is the movement of molecules from the area of their higher free energy to the area of the lower free energy.
Importance	1. Osmosis is important in animals for maintaining the water at the cellular level, also in transporting the nutrients, cell-cell diffusion. 2. In plants, it is helpful in maintaining the turgidity, provides mechanical support, prevents excess water loss, and responsible for absorption of water from the soil.	Diffusion is important in animals at the time of creating energy, during respiration it helps in exchange of gases, while in plants it is also helpful in the process of transpiration and photosynthesis.

Definition of Osmosis

The function of osmosis is to maintain the equilibrium on both the side of the membrane and so in this process there is the only movement of the water molecule, also called as the solvent.

In order to keep the homeostasis the water molecule move sidelong from higher water concentration to the region of lower water concentration. And also from the lower solute concentration to the higher solute concentration. Notably, the water molecules are passed through a semi-permeable membrane. So we can say that osmosis is a special kind of diffusion.

Osmosis is important in the distribution of nutrients and in a release of the metabolic waste from the body, and in maintaining the concentration gradient inside and outside the cell.

In plants osmosis is helpful in absorbing water from the soil, it helps in maintaining water level, even at the time of loss of water, cell to cell diffusion, also provide mechanical support.

Factors affecting osmosis are:

• Diffusion distance
• Concentration gradient.
• Temperature.

Osmotic pressure

It can be defined as the pressure exerted on the solution, to prevent the passage of the solvent into the solution, where both are separated by a semipermeable membrane.

Hypotonic Solution – Solution with relatively low pressure and high solvent concentration, here cells absorbs water, swell, and burst.

Hypertonic Solution – Solution with relatively higher osmotic pressure and high solute concentrations, here cells shrivel due to loss of water.

Isotonic Solution – Solution with equal osmotic pressure (iso-osmotic) and the concentration of solute and solvent are at level, so the cell tone is maintained and thus no changes in cell volume and shape.

Types of Osmosis are:

1. Reverse Osmosis.
2. Forward Osmosis.

Application of Osmosis

1. Transfusion – used in hospitals for the treatment of burns, dehydration, etc.
2. Fluid balance and blood volume – The fluid is balanced of each cell of the body due to the osmosis.
3. Edema due to hypoalbuminemia – Edema occurs due to the lower oncotic pressure of plasma, resulting in accumulation of fluid in tissue spaces.
4. Red blood cells and fragility – It prevent from rupturing the plasma membrane of the RBC, the condition called as hemolysis.

Definition of Diffusion

The movements of molecules like solid, gases or liquid, from the region of higher concentration to the region of lower concentration. The reason for this movement is the randomly moving molecules present in high concentration possess free energy, and when they move to the region of lower concentration, equilibrium of diffusing molecule along with the benefit of free energy is achieved. There is no role semi-permeable membrane.

Thus diffusion is important in creating energy, at the time of respiration it helps in exchange of gases in animals, it is also helpful in the process of transpiration and photosynthesis in plants.

Example: If a drop of blue ink is put in the jar filled with water, the ink will get evenly distributed all over the water, and the particles will get distributed everywhere, this is the simplest example of diffusion.

Another example to explain the diffusion is of any spray like deodorants, perfumes, so when they are used or opened, the molecules of gas get distributed equally at a certain available space.

Factors affecting diffusion are:

•  Molecular weight – Larger the molecular weight, slower will be the movement of the molecules.
•  Concentration gradient – Higher the difference, higher the rate of the motion of molecules
•  Pressure – Higher the pressure, lower will be the rate of diffusion due to the increase in the number of a collision.
•  Temperature – Higher the temperature, higher will be the motion of the particles.

Types of diffusion are:

1. Surface diffusion.
2. Collective diffusion.
3. Electron diffusion.
4. Facilitated diffusion.
5. Brownian diffusion.
6. Effusion.
7. Gaseous diffusion.
8. Photon diffusion.
9. Self-diffusion.
10. Reverse diffusion.
11. Momentum diffusion.
12. Knudsen diffusion.

Application of Diffusion

1. Few nutrients are absorbed in gastrointestinal tract through diffusion only, like minerals, vitamins, pentoses.
2. Exchange of gases such as oxygen and carbon dioxide in lungs and tissues occurs through diffusion only.
3. Passage of waste products in the renal tubules occurs due to diffusion.

Conclusion

So in general terms, we can say that the intermingling of the molecules, for maintaining the equilibrium is the naturally occurring process in the body, and are termed as osmosis and diffusion. Though this physical process is sometimes confusing also. But has a significant value in the field of science.

In order maintain the homeostasis of the body and also to balance between the various internal mechanisms through internal cellular functioning, these concepts are regularly compared and discussed. And so we can say that in the osmosis process only water molecule can show the motion across the semi-permeable membrane and in the diffusion liquids and gases can move.