Difference between Osmosis and Diffusion

Osmosis and diffusion are the two types of passive transport which play a vital role in moving molecules in and out of the cell.


Osmosis is the process of moving solvent particles across a semipermeable membrane from the solvent’s higher concentration to the solvent’s lower concentration. The complete process does not require energy to take place.

For example, the absorption of water molecules from the soil through the roots of the plant.

More to Explore: Reverse Osmosis


Diffusion is the process of moving particles from a region of higher concentration to a region of lower concentration until equilibrium is reached.  Simple diffusion does not require energy; however, facilitated diffusion requires ATP.

For example,  the aroma is diffused into the air by perfume sprays.

Read More: Diffusion

Difference between Osmosis and Diffusion

Osmosis Diffusion
It is limited only to the liquid medium. Occurs in liquid, gas and even solids.
Requires a semipermeable membrane. Does not require a semipermeable membrane.
Depends on the number of solute particles dissolved in the solvent. Depends on the presence of other particles.
Requires water for the movement of particles. Does not require water for the movement of particles.
Only the solvent molecules can diffuse. Both the molecules of solute and solvent can diffuse.
The flow of particles occurs only in one direction. The flow of particles occurs in all the directions.
The entire process can either be stopped or reversed by applying additional pressure on the solution side. This process can neither be stopped nor reversed.
Occurs only between similar types of solutions. Occurs between the similar and dissimilar types of solutions.
It involves the movement of only solvent molecules from one side to the other. It involves the movement of all the particles from one region to the other.
The concentration of the solvent does not become equal on both sides of the membrane. The concentration of the diffusion substance equalises to fill the available space.
Depends on solute potential. Does not depend on solute potential, pressure potential, or water potential.
Only water or another solvent moves from a region of its high concentration to a region of its lower concentration. Any type of substance moves from area of highest energy or concentration to region of lowest energy or concentration.
Not associated with uptake of minerals and nutrients. It helps in the uptake of minerals and nutrients.

Further Reading: Cell Wall


To incorporate the movement of molecules in and out of the cell, two types of transport systems exist, namely osmosis and diffusion. These two systems are passive transport systems as they do not require any additional energy to function (however, facilitated diffusion requires ATP). The primary differentiating factor between the two systems is the medium in which they are employed. Osmosis can only function in a liquid medium, but diffusion can occur in all three mediums (solid, liquid and gas). Furthermore, osmosis requires a semi-permeable membrane, while diffusion does not. The intake of water in plants is an example of osmosis. Diffusion is observed when a drop of food colouring is added to a glass of water, where eventually, the entire water content becomes coloured.

Extended Reading: Passive Transport

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  1. Clearly was able to understand. Thanks a lot!!!!

  2. Thanks. It helped me a lot.