Diffusion Definition

“Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration down the concentration gradient.”

Read on to explore what is diffusion and the different types of diffusion.

What is Diffusion?

Diffusion is the process wherein the molecules merge as a result of their kinetic energy of random motion. It occurs in liquids and gases because their molecules move randomly. The molecules move from a region of higher concentration to a region of lower concentration, down the concentration gradient, until the concentration equalizes throughout the medium.


For instance:

Take a beaker filled with water. Add a few crystals of copper sulfate carefully and leave the unit undisturbed for some time. We can observe that the water in the beaker is uniformly coloured. In this experiment, both copper sulfate and water diffuse independently. Hence concentration gradient would be nothing other than the process by which particles known by the name of solutes travel through a solution from a higher particle numbered area to a lower-numbered area.

Also Read: Diffusion in Plants

Types of Diffusion

Since distribution occurs in a variety of conditions, following are the terms that specify different types of diffusion. Simple diffusion and facilitated diffusion are two different types of Diffusion

Simple diffusion

A process in which the substance moves through a semipermeable membrane without any help from transport proteins.  For example, bacteria delivers small nutrients, water, and oxygen into the cytoplasm through simple diffusion.

Facilitated diffusion

Facilitated diffusion

Facilitated diffusion is a passive movement of molecules across the cell membrane from the region of higher concentration to the region of lower concentration by means of a carrier molecule.

Dialysis: It is the diffusion of solutes across a selectively permeable membrane. A selectively permeable membrane is the one that allows only specific ions and molecules to pass through, while obstructs the movement of others.

Osmosis: It is the movement of solvent molecules from the region of higher concentration to the region of lower concentration through a semipermeable membrane.  Since water is solvent in every living being, biologists define osmosis as the diffusion of water across a selectively permeable membrane. For example, plants take water and minerals from roots with the help of osmosis.


Factors Affecting Diffusion

There are a few factors that affect the process of diffusion, which individually and collectively alters the rate and extent of diffusion. These factors include:

  • Temperature.
  • Area of Interaction.
  • Size of the Particle.
  • The steepness of the concentration gradient.

Examples of Diffusion

  • A teabag immersed in a cup of hot water will diffuse into the water and change its colour.
  • A spray of perfume or room freshener will get diffused into the air by which we can sense the odour.
  • Sugar gets dissolved evenly and sweetens the water without having to stir it.
  • As we lit the incense stick, its smoke gets diffused into the air and spreads throughout the room.
  • By adding boiling water into the dried noodles, the water diffuses causing rehydration and making dried noodles plumper and saturated.

Causes of Diffusion

Diffusion is a natural and physical process, which happens on its own, without stirring, shaking or wafting the solutions. In gases and liquids, particles move randomly from one place to another, during which the particles collide with each other or with the container. This changes the direction of the molecules.

Significance of Diffusion

Diffusion is an important process, which is involved in the different life processes. As mentioned above, it is the net movement of particles, ions, molecules, solution, etc. In all living species, diffusion plays an important role in the movement of the molecules during the metabolic process in the cells.

Diffusion is important for the following reasons:

  • During the process of respiration, this process helps in diffusing the carbon dioxide gas out through the cell membrane into the blood.
  • Diffusion also occurs in plant cells. In all green plants, water present in the soil diffuses into plants through their root hair cells.
  • The movement of ions across the neurons that generates electrical charge is due to diffusion.

Also Read: Difference between diffusion and osmosis

Learn more about what is diffusion, its definition, types, examples, and other related topics @ BYJU’S Biology

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