Home | Biology | Diffusion Explained – Types, Examples and Factors

Diffusion Explained – Types, Examples and Factors

May 4, 2023
written by Sidra Batool

What is Diffusion?

Diffusion is the movement of molecules from an area of high concentration to an area of low concentration, which is caused by their random motion.

A common example is the scent of perfume spreading through a room as molecules disperse into the air.

Diffusion Definition in Biology

In biology, diffusion is essential for transporting substances in and out of cells. Molecules like oxygen and carbon dioxide move across cell membranes from areas of higher concentration to lower concentration until equilibrium is reached.

Diffusion Definition in Chemistry

In chemistry, diffusion influences the rate of chemical reactions. Different substances, whether solids, liquids, or gases, diffuse at different rates, affecting how quickly reactions occur.

Diffusion Definition in Physics

In physics, diffusion is the movement of particles and energy transfer. For example, heat conduction involves thermal energy diffusing from warmer areas to cooler ones. This principle also applies to neutron diffusion in nuclear reactors.

[Reference]

image showing what is diffusion
What is diffusion

In humans, movement of oxygen and carbon dioxide between the alveoli in the lungs and the surrounding capillaries occurs through diffusion. Oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli to be exhaled.

Read Difference Between Diffusion and Osmosis

Principles of Diffusion

Diffusion is how molecules naturally move and spread out in any substance. It happens because molecules are always moving randomly, bouncing around and bumping into each other. These molecules move from areas where they are crowded to places where there are fewer molecules.

No extra energy is needed for this movement. it just happens by itself. For instnace, a tea bag in water – the color spreads out naturally without stirring. The bigger the difference in concentration between two areas, the faster molecules will move.

This movement keeps happening until the molecules are evenly spread out everywhere. Even when they are evenly spread, the molecules keep moving, but we don’t see any more changes because there are the same number of molecules everywhere. This process happens in gases, liquids, and even in our body’s cells.

Types of Diffusion

There are different types of diffusion that occur in biological systems:

image showing types of diffusion

Simple diffusion

Simple diffusion is the movement of molecules from an area of high concentration to an area of lower concentration without the need for a membrane or carrier protein.

This type of diffusion is typically used for small nonpolar molecules, such as oxygen and carbon dioxide, which can diffuse easily through cell membranes via simple diffusion.

Facilitated diffusion

Facilitated diffusion involves the movement of molecules across a membrane from an area of high concentration to an area of lower concentration, with the help of a membrane protein.

This process is used for larger or polar molecules, such as glucose and amino acids, which cannot diffuse across the membrane through simple diffusion.

Osmosis

Osmosis is a special type of diffusion that refers to the movement of water molecules across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.

This process is important in maintaining the proper balance of water and solutes in biological systems, such as the kidneys and plants.

Examples of diffusion in chemical and biological processes

Here are the examples of diffusion in Biology and Chemistry:

  • Movement of gases through a membrane (e.g., oxygen and carbon dioxide exchange in the lungs)
  • Mixing of solutions (e.g., sugar dissolving in water)
  • Transport of nutrients in biological systems (e.g., glucose moving from the bloodstream into cells for energy production)

Factors affecting Diffusion

The rate of diffusion is controlled by several factors:

Concentration Gradient

A concentration gradient shows how many molecules are in different areas. When there’s a big difference between two areas, molecules move faster from the crowded area to the less crowded area.

Temperature

Higher temperatures make molecules move faster. This speeds up the rate of diffusion in any substance.

Surface Area

More surface area means molecules have more space to move through. This makes diffusion happen more quickly across the available space.

Molecular Size

Smaller molecules move more easily through spaces than larger ones. They can diffuse more quickly because of their smaller size.

Density

The density of the medium affects how molecules move. In denser materials, molecules interact more with each other as they move.

[Reference]

image showing factors affecting diffusion

Also Learn About:

Why is Diffusion Faster in Hot Water?Why is Diffusion Faster in Small Cells?
Why is Diffusion Faster in Liquids than Solids?Why is Diffusion Faster in Lungs?
Why is Diffusion Faster in Air Than Water?Why is Diffusion Faster in Gases?
Why Is Diffusion Faster In Water Than in Agar?How Does Temperature Affect Diffusion In Biology?
Why Does Diffusion Occurs?

FAQs

What is the definition of diffusion?

Diffusion is a process of movement of molecules (solids, liquids, gases) from higher concentration to lower concentration.

Why is it called diffusion?

The word “Diffusion” was derived from a Latin word “diffusionem, diffusio” meaning “to spread out/or pouring forth”. That’s why it is called diffusion as solute molecules spread out in solvent.

Who discovered diffusion?

Thomas Graham discovered the phenomenon of diffusion in gases for the first time.

File Under: