Diffusion and Osmosis

Why is Osmosis And Diffusion Important To Living Organisms

There are several processes which can be performed as an experiment in a lab also such processes do pre-exist in our body as well as natural and are in function in order to maintain the proper functioning of the body and nature. Out of many such processes, diffusion and osmosis are the most discussed one. In this chapter we are going to learn about diffusion and osmosis separately and in detail, we will also learn about the significance of diffusion and osmosis about how they are different or similar to each other and also though these two are different processes but you will be surprised to know that osmosis is a special kind of diffusion. We will learn about all of this further in the chapter. So let's get started with osmosis.


Osmosis refers to a process in which solvent particles (water molecules) move from a dilute solution into a concentrated solution across a semipermeable membrane. Osmosis occurs in order to dilute the concentrated solution and also to ensure the equalization of concentration on both the sides of the membrane.

Let's understand this process more deeply with the help of a diagram which is given below:

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The top figure shows us the semi-permeable membrane in between the sugar solution and water which separates the two. Because the sugar molecules are large and cannot pass through the membrane, water molecules from solvent permeate to the other side of the membrane and equilibrium is attained as seen in the figure at the bottom.

Examples of osmosis

  • The roots of the plant absorbing water is a natural example of osmosis.

  • The swelling up of red blood cells, when exposed to fresh water, is another example of osmosis.


Diffusion refers to the process in which particles from a higher concentration tend to move or transport to a lower concentration medium in order to attain the equilibrium. In diffusion, the concentration is equalized throughout the medium. Now we will try to understand this process of diffusion with the help of a diagram given below 

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As we can see in the diagram dye molecules are added to the water molecules and later when the mixture is kept undisturbed for some time water molecule ad well as the dye molecules tend to diffuse independently.

Types of Diffusion

There are two types of diffusion namely

  • Simple diffusion

  • Facilitated diffusion

Let's Understand Simple Diffusion First

In simple diffusion, the substances move through the semipermeable membrane without any help of a transporter. A transporter can be anything like a bacteria.

While Facilitated Diffusion Refers to:

Movement of molecules from a higher concentrated substance to the lower concentrated substance with the help of a transporter or a carrier molecule across the cell membrane.

Examples of Diffusion

  • Have you ever added a drop of food colour to water? If not, try it today you will be amazed at the results and you will be able to see an example of diffusion right in front of your eyes.

  • When a food colour drop is added to the water the entire solution turns into the colour of food colour which shows that molecules of both water and food colour diffuse independently.

  • Another example of diffusion is the scent of perfume occupying the entire room gradually.

Significance of Diffusion and Osmosis

Both diffusion and osmosis are really important as these ensure the equalization of forces inside cells and also inside an organism as a whole by spreading all the necessary chemicals and nutrients from highly concentrated area to the low concentration area inside an organism

Similarities between Osmosis and Diffusion

Both of these processes we discussed are similar in many ways. Let's have a look at similarities between these two processes.

  • Both of these processes, diffusion and osmosis tend to equalize the concentration of the solution.

  • Both of these processes do not require any extra energy or input hence these are called passive processes.

  • Both of these processes observe the movement of molecules from higher concentration area to lower concentration area.

Differences Between Osmosis and Diffusion



Movement of any type of substance is possible from a higher concentration area to lower concentration area 

Only solvent (generally water) can move from the area of higher concentration to an area of lower concentration.

Solid, liquid or gas, diffusion can take place in any of these media.

Osmosis can take place only in a liquid medium

No requirement of semi-permeable membrane for diffusion to occur.

Semi-permeable membrane is a must for osmosis to take place.

There is the equalization of concentration to occupy the available space

Both sides of the membrane does not have equal concentration

In diffusion, there is no dependency on solute potential, water potential or pressure potential

There is dependency on solute potential in osmosis

Diffusion depends upon the presence of other particles

Osmosis depends upon the number of the solute particles which are dissolved into the solvent

Movement or transportation in diffusion tends to equalize the concentration throughout

Movement or transportation in this process of osmosis tends to equalize the concentration of the solvent, which doesn't occur although.

FAQ (Frequently Asked Questions)

1. Osmosis is a special kind of diffusion. Comment.

Osmosis is the movement of water molecules or solvent from a higher concentration area to a lower concentration area through a semipermeable membrane. While diffusion refers to the process in which substances get transported from an area of higher concentration to an area of lower concentration without any semi-permeable membrane. Now in osmosis, the solvent (water molecule) diffuses from high concentrated area to low concentrated area hence osmosis is referred to as a special kind of diffusion.

2. Why is osmosis and diffusion important to living organisms

Both the processes, diffusion and osmosis work in the companionship of each other inside of living organisms in order to attain the equalizing effect. They attain this equalizing effect by spreading and transporting nutrients, water and other necessary chemicals from the areas of higher concentration to areas of lower concentration inside a body. This process is called moving down of concentration gradient.