14 Difference Between Diffusion And Osmosis (With Examples & Comparison Chart)

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What Is Diffusion?

Diffusion is a physical process that refers to spontaneous movement of particles from a region of high concentration to a region of low concentration. Concentration refers to how much a particular object or particle is in a given space. Gasses and molecules in a liquid have a tendency to diffuse from a more concentrated environment to a less concentrated environment.

The overall goal of diffusion is for the particles or objects to reach equilibrium. Equilibrium is when the amount of the particles or objects is the same throughout a solution or is equally dispersed throughout a given area. The two main types of diffusion are:

  • Simple diffusion
  • Facilitated diffusion

Factors Affecting Diffusion

  • Temperature:  Increase in temperature increases the kinetic energy of particles that eventually result to increase in their velocity.  This high velocity leads to high rate of diffusion.
  • Surface area: The larger the surface area the higher the number of particles that will be able to move in a given time so the faster the rate.
  • Medium of diffusion: Presence of particles in a medium of diffusion acts as a barrier to diffusion. The more the particles the lower the rate of diffusion, the lower the particles the higher the rate of diffusion.
  • Density of diffusing substance:  The higher the density of the diffusing substance, the lower the rate of diffusion, the lower the density the higher the rate of diffusion.
  • Concentration gradient: Concentration gradient is the number of solute molecules that can be found within a given volume. Generally, the greater the concentration gradient, the greater the rate of diffusion.

What You Need To Know About Diffusion

  1. Diffusion is a spontaneous movement of particles from a region of high concentration to a region of low concentration.
  2. Diffusion can occur between any medium such as gas to gas, liquid to liquid, liquid to gas, solid to gas and solid to liquid.
  3. The motion of particles is direct and does not require a semi-permeable membrane.
  4. Diffusion process can neither be opposed nor reversed.
  5. Hydrostatic or turgor pressure does not normally operate in diffusion.
  6. Diffusion can occur between similar or different types of solvents.
  7. At the end of diffusion process, the concentration of the diffusing particles will be equalized.
  8. In diffusion, the flow of particles can occur in all directions.
  9. Diffusion of a substance is largely independent of the presence of other substances.
  10. Diffusion is purely dependent upon the free energy of the diffusing molecules/substance.
  11. Diffusion is not influenced by the solute potential.
  12. Diffusion helps in exchange of gases during respiration, photosynthesis and transpiration.
  13. The two main types of diffusion are simple diffusion and facilitated diffusion.
  14. The movement in diffusion is to equalize concentration (energy) throughout the system.

Examples Of Diffusion

  • A teabag immersed in a cup of hot water will diffuse into the water and change its color.
  • A spray of perfume or room freshener will get diffused into air by which we sense the odor.
  • Sugar gets dissolved evenly in tea and sweetens the tea without having to stir it.
  • Smoke from cigarette gets diffused into the air and spreads throughout the room. 

Importance Of Diffusion

  • During respiration, diffusion helps in diffusing the carbon dioxide gas out through the cell membrane into the blood.
  • In all plants, water present in the soil diffuses into plants through their root hair cells.
  • The movement of ions across the neurons that generate electrical charge is due to diffusion.
  • Food coloring in water diffuses until it’s evenly distributed throughout the liquid.

What Is Osmosis?

 Osmosis is a spontaneous movement of solvent molecules from a region of low concentration to a region of high concentration across a semi-permeable membrane, the result of which there will be an equalizing of solute concentration on either side of the membrane.

Osmosis deals with chemical solutions. Solutions have two parts, a solvent and a solute. When solute dissolves in a solvent, the end product is referred to as a solution. Salt water is an example of a solution; salt is a solute and water is the solvent.  If two solutions of different concentration are separated by a semi-permeable membrane, then the solvent will tend to diffuse across the membrane from the less concentrated to the more concentrated solution. In as far as osmosis is concerned; a solution is classified as hypotonic hypertonic, and isotonic.

Hypotonic solution is a highly concentrated solution, whereas isotonic solution is an equally concentrated solution while hypotonic solution is a lowly concentrated solution.

The two main types of osmosis are:

  • Endosmosis (the osmotic entry of water into a cell, organ or system).
  • Exosmosis (the osmotic withdrawal of water from a cell, organ or system).

The direction and rate of osmosis depends upon the sum of two forces, pressure gradient and the concentration gradient. The net force or gradient is determined by the difference in the water potentials of the solutions separated by a semi-permeable membrane.

What You Need To Know About Osmosis

  1. Osmosis is a spontaneous movement of solvent molecules from a region of low concentration to a region of high concentration across a semi-permeable membrane.
  2. Osmosis can occur only through a semi-permeable membrane.
  3. The motion of molecules is through the semi-permeable in osmosis.
  4. Osmosis can be reversed or stopped by pressure application on the solution side.
  5. Osmosis is opposed by turgor or hydrostatic pressure of the system.
  6. Osmosis can take place only between similar types of solvents.
  7. At the end of osmosis, the concentration of the solvent will not be equalized.
  8. In osmosis, the flow of particles occurs only in one direction.
  9. Osmosis is dependent upon the number of particles of other substances dissolved in liquid.
  10. Osmosis is dependent upon the degree of reduction of free energy of one solvent over that of another.
  11. Osmosis is influenced by the solution potential.
  12. Osmosis influences the distribution of nutrients and release of metabolic waste products. In plants, osmosis is partially responsible for absorption of soil water and for the elevation of liquid to the leaves of the plant.
  13. The two main types of osmosis are Endosmosis and Exosmosis.
  14. The movements in osmosis seek to equalize solvent concentration, although it does not achieve this.

Examples Of Osmosis

  • An example of osmosis is the movement of water into root hair cells.
  • Swelling of red blood cells when placed in freshwater

Biological Importance Of Osmosis

  • Living cells remain distended or turgid only by the osmotic entry of water into them.
  • Osmosis significantly contributes to the regulation of blood volume and urine excretion
  • Fluid balance of the different compartments of the body is maintained due to osmosis.
  • Plants absorb large quantity of water from the soil by their root by the process of osmosis.
  • Cell to cell movement of water takes place by osmosis.
  • It helps young seedlings to come out of the soil.
  • It controls opening and closing of stomata during transpiration through its regulation of the turgidity of guard cells.

Also Read: Difference Between Active And Passive Transport

Difference Between Diffusion And Osmosis in Tabular Form

BASIS OF COMPARISON DIFFUSION OSMOSIS
Description Diffusion is a spontaneous movement of particles from a region of high concentration to a region of low concentration.   Osmosis is a spontaneous movement of solvent molecules from a region of low concentration to a region of high concentration across a semi-permeable membrane.  
Occurrence Diffusion can occur between any medium such as gas to gas, liquid to liquid, liquid to gas, solid to gas and solid to liquid.   Osmosis can occur only through a semi-permeable membrane.  
Motion of Particles The motion of particles is direct and does not require a semi-permeable membrane.   The motion of molecules is through the semi-permeable in osmosis.  
Stoppage/ Reversal Diffusion process can neither be opposed nor reversed.   Osmosis can be reversed or stopped by pressure application on the solution side.  
Hydrostatic And Turgor Pressure Hydrostatic or turgor pressure does not normally operate in diffusion.   Osmosis is opposed by turgor or hydrostatic pressure of the system.    
Occurrence Diffusion can occur between similar or different types of solvents.   Osmosis can take place only between similar types of solvents
At The End Of Process At the end of diffusion process, the concentration of the diffusing particles will be equalized.   At the end of osmosis, the concentration of the solvent will not be equalized.
Flow Of Particles In diffusion, the flow of particles can occur in all directions In osmosis, the flow of particles occurs only in one direction.  
Dependency Diffusion of a substance is largely independent of the presence of other substances. Osmosis is dependent upon the number of particles of other substances dissolved in liquid.
Free Energy Diffusion is purely dependent upon the free energy of the diffusing molecules/substance.   Osmosis is dependent upon the degree of reduction of free energy of one solvent over that of another.  
Solute/Solution Potential Diffusion is not influenced by the solute potential.   Osmosis is influenced by the solution potential.
Importance Diffusion helps in exchange of gases during respiration, photosynthesis and transpiration.   Osmosis influences the distribution of nutrients and release of metabolic waste products. In plants, osmosis is partially responsible for absorption of soil water and for the elevation of liquid to the leaves of the plant.  
Types The two main types of diffusion are simple diffusion and facilitated diffusion. The two main types of osmosis are Endosmosis and Exosmosis.  
Goal The movement in diffusion is to equalize concentration (energy) throughout the system.   The movements in osmosis seek to equalize solvent concentration, although it does not achieve this.  

Also Read: Difference Between Simple And Facilitated Diffusion

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