3 Types of Diffusion (Plus Examples for Each) (2023)

Diffusion is the physical process of the natural movement of ions or molecules. It occurs in both liquids and gasses and is important to all living organisms for many different reasons.

First of which is survival. Diffusion makes the nervous system function, promotes cellular respiration, and allows nutrients to be distributed among cells, among many others.

We may not be aware of it, but diffusion is ever-present in our lives. Get to know more about this molecular process and how we benefit from it every day.

Main Types of Diffusion

Passive Diffusion

This type of diffusion occurs when molecules move across a semipermeable membrane, without the protein channels helping the movement take place. Cell membranes are made out of a bilayer made of phospholipid, which has a middle layer that is nonpolar, or water-fearing. The middle layer is protected on both sides by water-loving, or polar hydrophilic surfaces.

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Hydrophobic molecules always pass easily through a cell membrane, and this includes certain gases such as carbon dioxide, oxygen, and nitrogen. Electrically charged, large polar molecules are unable to pass freely through a cell membrane.

When diffusion occurs across a cell membrane, this is considered a type of passive transport, and it requires no energy. Keep in mind that the cell membrane is a phospholipid bilayer and that both the inside and outside of the cell are water-based.

There is also a hydrophobic area in the middle, which is a vital barrier to anything that is charged and large, or hydrophilic. Simple diffusion allows the molecules that are hydrophobic to pass through the cell membrane, much like the hydrophobic region.

Because of this, simple diffusion provides unassisted passage of hydrophobic, nonpolar molecules that are quite small, and the passage starts at a higher concentration and goes to a lower concentration. Even if the cells are hydrophilic, tiny molecules can still slip through the membrane of the cell, simply because of their small size.

Facilitated Diffusion

Facilitated diffusion allows for the flow of molecules down a concentration gradient and across the cell’s membrane, but the process requires help from a protein. Two categories of proteins exist that help this type of diffusion.

The first are carrier proteins, which can be thought of like a taxi cab in a cell membrane because they shuffle the molecules from one side of the membrane to the other side.

The second is channel proteins, which resemble tunnels and create a hole across the cell membrane. In these cases, channels open which allow the molecules to flow through them. Although facilitated diffusion involves proteins, the proteins involved require no use of the energy molecule known as ATP.

(Video) Grid Cloth Diffusion - What Makes it So Good?

Molecules such as oxygen and carbon dioxide can diffuse across the plasma membrane directly, while other molecules need assistance to cross the hydrophobic core.

In facilitated diffusion, the molecules diffuse across the plasma membrane with help from the proteins of the membrane, including proteins such as carriers and channels. Because a concentration gradient exists for those molecules, they have the potential to diffuse either out of or into the cell itself by moving down through it.

Because they are polar or charged, however, they are unable to cross the phospholipid part of the membrane without a little assistance. In other words, the proteins that are part of the facilitated transport actually protect the molecules from the hydrophobic core of that membrane, which provides a route that they can cross.

In summary, the two major classifications of proteins for facilitated transport are carrier proteins and channels.

Channel Diffusion

Some experts list three types of diffusion instead of two: simple, channel, and facilitated. In these descriptions, channel diffusion is considered a passive process that involves the ions and charged particles moving through a specific channel protein or pore in the wall of the cell.

In this case, no limits to the number of particles that travel through each of those channels exist. The proteins are actually embedded in the cell membrane, and they can open and close, which allows the compounds or molecules to go into or out of the cell. This type of diffusion is regulated very easily by the proteins of the membrane.

Details to Help You Understand Diffusion

The Difference Between Diffusion and Osmosis

Osmosis is a specific type of diffusion that consists of water crossing a semipermeable membrane and going into an area that has greater solute concentration. By contrast, standard diffusion often lets both solutes and solvents move freely towards equilibrium.

As a general rule, diffusion involves the net movement of molecules in a solution with a higher concentration to an area of a lower concentration. Osmotic pressure has the potential to be very powerful, and it is the only force that is required to move water from the very lowest roots to the tops of the tallest trees anywhere in the world.

If water dissolves any other substance, it is usually because the water’s molecules, which are polar, and the solute are actually attracted to one another. Each ion, atom, or molecule of solute has a charge in a minimum of one region which attracts one or another side of the water molecule.

Molecules are in random and constant motion around one another when they’re in the liquid water, but because of this attraction, the water molecules are a tiny bit more likely to move towards water molecules, rather than other solvent particles.

This is a net movement that gradually results in a more even distribution of the solute. In the process of osmosis, only the water molecules can move and equalize concentrations.

Osmosis and diffusion are, in fact, related but are not the exact same thing. With diffusion, molecules move from a high-concentration area to a low-concentration area, whereas osmosis is simply the diffusion of water across any type of semipermeable membrane.

Both processes have to do with molecules moving down a concentration gradient; however, the term “osmosis” refers to the movement of water molecules specifically, while diffusion can also involve any other type of molecules.

(Video) Passive Transport: Diffusion, Facilitated Diffusion & Osmosis (Difference)

Diffusion and osmosis are both spontaneous in nature, which simply means that they occur without the assistance of any type of outside energy. “Osmosis” essentially refers only to the movement of water which is in a liquid state, but the term “diffusion” can also mean the movement of molecules either in a gaseous or a liquid state.

An example includes when carbon dioxide gas gets released into the center of a room, and it subsequently diffuses throughout that room until the carbon dioxide concentration is even and uniform across the entire room.

The term “osmosis” is frequently used in sciences such as physiology and cell biology. If the cell is placed in a hypertonic solution or a solution with a higher concentration of solute than that which is found inside of the cell, it results in water moving out of the cell spontaneously – or osmosis.

In both of these cases, it is easy to say that the diffusion of water actually occurred across the membrane of the cell.

Examples of Types of Diffusion

Some examples of different diffusion types include:

  • When the tea is dispersed in hot water
  • When smoke from a lit cigarette is spread around in the air
  • When bubbles of carbon dioxide diffuse from an opened soda bottle and cause the soda itself to become flat as the carbonation is lost
  • When food is digested, which is caused by oxygen being transferred into the blood from the lungs and into the muscles from the cells of the blood
  • When a woman is pregnant and food and oxygen travel from the mother’s body into the fetus
  • When a hot liquid such as coffee is being poured, and the cup is heated because the heat actually diffuses
  • When you place a sugar cube into a liquid and it dissolves, because it is actually diffusing through the liquid and sweetening it evenly, even if you aren’t stirring it
  • When you deflate a helium balloon because it deflates when it loses helium slowly from the balloon
  • When you smell perfume or cologne on another human being because the perfume or cologne is diffusing into the air around it
  • When you water your plants, the water is diffused into them and prevents the leaves from wilting; in other words, the carbon dioxide is diffused from the leaves from air pockets located between the various mesophyll cells and transfers it to the chloroplast
  • When warm waters around the equator are diffused by ocean currents, and if you’re in an area where the air that is moist and warm rises within the air that is cold, that water vapor can turn into rainstorms

Passive Diffusion

Examples of passive, or simple diffusion include:

  • Carbon dioxide. Carbon dioxide is very small, and the molecule can be dissolved in water. One example of this is the burning sensation that you get when you hold your breath, which results in a strong desire to breathe. This happens because carbon dioxide accumulates in the nerve tissues of your bloodstream, which are very sensitive, as well as in your brain and lungs. Once you start to breathe again, carbon dioxide starts to diffuse out of your system. Moreover, many gases can do this because your lungs diffuse gases such as nitrogen, oxygen, and many others during processes such as this one.
  • Bacteria. Bacteria are simple organisms that have no way to intake nutrients unless they diffuse them across the cell membrane. Bacteria do not use facilitated diffusion to transport most of these nutrients, but instead, they rely on simple diffusion to deliver water, oxygen, and small nutrients to the cytoplasm. There are no specialized organelles with their cells to transport or hold substances, and therefore the bacteria rely on the simple diffusion of the various materials contained in their cells to guarantee that those materials are present for the reactions that control all of their life processes.
  • Oxygen. The eighth element of the periodic table, it is a good example of a molecule that is transported using passive diffusion. When combined with glucose to produce carbon dioxide, oxygen plays a very important role in the respiration process, which uses passive diffusion to complete.
  • Steroid hormones. This is a great example of simple diffusion. Steroid hormones are similar to cholesterol and they can move freely across different membranes if it is down their concentration gradient. Steroids will bind to a hormone-binding site that prevents a certain binding complex from attaching to a specific DNA binding domain, which results in the DNA binding site being exposed, triggering the transcription-activating domain and altering gene transcription.

NOTE: To learn about active transport, check out our article “7 Different Types of Active Transport”

Facilitated Diffusion

One example of facilitated diffusion is when K+ ions are passed through a membrane and they are aided by a potassium transport protein, as well as glucose and amino acids that are passed with the assistance of proteins known as permeases.

Retinol-binding protein can act as a water-soluble carrier for fatty acids and retinol. Carrier proteins are molecule specific and therefore, the diffusion rate is always limited by the number of carriers. When all carriers for a particular molecule are occupied, the so-called saturation point is reached.

Substances that utilize facilitated diffusion include:

  • The skin of a cell. The plasma membrane is a very thin layer that maintains the cell’s integrity and encloses the cell itself, mostly by containing cellular fluid, or cytoplasm, and organelles, which are specialized structures. The plasma membrane regulates all of the substances that enter or leave the cell’s interior. Cells move molecules through the cell through a variety of methods, including two general categories – active transport and passive transport. Cells have to expend energy in order to accomplish active transport, whereas passive transport requires no cellular energy. Passive transport includes the activity of facilitated diffusion.
  • The facilitation of glucose. Glucose is a sugar molecule and is the main energy source for many types of cells. Outside of a cell, a person’s bloodstream is constantly supplying glucose, while cellular metabolism continuously consumes glucose on the inside of the cell. What results is a concentration of glucose located outside of the cell, which stays at a higher concentration level inside of the cell. Nevertheless, the glucose molecule is too big to get through the plasma membrane without assistance. Because this is so, the cell provides glucose specific carrier proteins that actually stick to glucose molecules, allowing them to enter the cell.
  • Molecules flow from high to low. Since some molecules, during the diffusion process, are unable to enter or exit a cell while being influenced by a concentration gradient because they are incompatible with the cell’s plasma membrane, facilitated diffusion can assist some of these molecules when they’re trying to pass through the plasma membrane. They do this by binding the molecules to special carrier proteins or by the opening of channels located between the cell and the surrounding environment.
  • Ion channels. Carrier proteins being used for facilitated diffusion is quite common, and some examples include galactose and fructose, which are monosaccharides just like glucose is; amino acids, which make up a protein’s building blocks; and nucleosides, what is required for the synthesis of RNA and DNA to occur. There is a different type of facilitated diffusion that involves channel proteins. These proteins don’t bind to molecules, but instead, they open a channel which allows smaller molecules and ions – such as potassium, calcium, sodium, and chlorine – to transport quickly.
  • General reasons for facilitated diffusion. There are a few polar, very large molecules that are lipid-insoluble or electrically charged which require help in order to diffuse across the membrane of the plasma. In these instances, facilitated diffusion which uses ion channels or carrier proteins allow these important molecules – for example, glucose – to actually cross the membrane.

Channel Diffusion

(Video) Relocation & Expansion Diffusion [AP Human Geography Unit 3 Topic 4] (3.4)

In channel diffusion, the materials pass through one end, and the ion channels open and let them pass through if solutes are also present. It is a diffusion that is carried out by a protein channel, and therefore it is also called a channel-mediated diffusion. A lot of molecules have to have help moving across the cell membrane, thanks to their polarity and size.

The proteins that are embedded in the membrane act as a gateway for diffusion. Molecules will move down a concentration gradient via a protein pore that is open, which is a process called channel diffusion. There are many practical examples of channel diffusion available, and there are many websites that go into great detail on this topic.

Glossary of Terms Related to Diffusion

Active Transport:Active transport is a process that requires energy and in which there is a movement of ions or molecules that goes against a concentration gradient; it goes from an area of low concentration to one that has a high concentration.

Active Transport Occurrences:Active transport can only occur in a living tissue where there is energy from the ATP present. Active transport allows cells to take up ions or nutrients even with low concentrations of substances outside of the cell; allows the cells to get rid of substances that are unwanted when the concentration is greater outside of the cell; in plant cells, the phloem is actively loaded with sucrose; enables the Na/K pump to work with ions which move in opposite directions; enables a Ca pump to work at neuromuscular junctions in order for the muscles to contract; and in the kidney, useful substances such as ions, are reabsorbed against the concentration gradient.

Cell-Mediated Endocytosis:This occurs when molecules bind to special receptors in the membrane and are then taken into the cell via a vesicle that is created by the plasma membrane itself.

Crenation:When red blood cells dehydrate.

Dialysis:A process whereby the blood is filtered in order to remove toxins.

Diffusion:The movement of a molecule from its higher to its lower concentration, until it reaches equilibrium.

Endocytosis:This refers to the bulk importation of various substances into the cells.

Endocytosis Process:During this process, molecules are actually too big to fit through the membranes.

Endocytosis Types:The three main types of endocytosis are phagocytosis, pinocytosis, and cell-mediated endocytosis.

Exocytosis:This refers to the bulk secretion of large molecules from the cells.

Exocytosis Process:This process occurs when molecules are packed into Golgi vesicles or lysosomes by the Golgi and the vesicles then move into the cell surface membrane, with help from macro tubules and ATP. They then fuse with the plasma membrane and release the contents to the exterior.

Facilitated Diffusion:In facilitated diffusion, the molecules pass through either channel or carrier proteins located in the membrane, and the movement of the molecules is facilitated by a protein. In addition, the molecules are moving down their concentration gradient in facilitated diffusion, not up the gradient.

(Video) Facilitated Diffusion Explained

Facilitated Diffusion Differences:The two main differences are: with channeled proteins, there is no opening and closing, and there is no binding site; when it comes to carrier proteins, they do open and close, and there is always a binding site.

Facilitated Diffusion Types

There are two types of facilitated diffusion – carrier proteins and channeled proteins

Hemolysis: Refers to a situation whereby a red blood cell takes in the maximum amount of water and therefore, it bursts.

Hydrostatic Pressure:Liquid pressure.

Hypertonic:Low water potential.

Incipient Plasmolysis:When half, or 50% of cells, are considered slightly plasmolyzed.

Isotonic:Equal on both sides.

Molecules That Pass Through Facilitated Diffusion:Only large polar molecules pass through facilitated diffusion, including amino acids, glucose, and nucleotides.

Molecules That Pass Through Simple Diffusion:Only small molecules can pass through simple diffusions, such as H2O, O2, and CO2.

Osmosis:Osmosis is the passive movement of water molecules from an area with a low solute concentration to one that has a high solute concentration through a membrane that is semipermeable.

Phagocytosis:Also known as cell eating, phagocytosis refers to the process whereby large molecules are taken into a phagocytic vacuole where they are then digested. The vacuole is called a phagosome.

Pinocytosis:Pinocytosis refers to the process whereby molecules are taken into a vesicle that has been formed by the membrane of the plasma; also referred to as cell drinking.

Plasmolysis:Plasmolysis describes when plant cells are exposed to an outward osmotic flow of water, which results in the shrinking of the cytoplasm, shrinking it away from a living cell wall.

Simple Diffusion:In simple diffusion, very small molecules have the capability to move through gaps that are located between the various phospholipid molecules in the cell membranes.

(Video) Diffusion-Real Life Examples

Turgid:This is when a plant cell has taken in the maximum amount of water.

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What are the 3 examples of diffusion? ›

Some examples of diffusion that occurs in our daily life are given below.
  • The smell of perfumes/Incense Sticks.
  • Opening the Soda/Cold Drinks bottle and the CO2 diffuses in the air.
  • Dipping the tea bags in hot water will diffuse the tea in hot water.
  • Small dust particles or smoke diffuse into the air and cause air pollution.

What is diffusion and examples? ›

diffusion, process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration. A familiar example is the perfume of a flower that quickly permeates the still air of a room.

How does diffusion occur 2 examples? ›

A tea bag 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.

What are the different type of diffusion? ›

The three main types of this phenomenon are expansion diffusion, stimulus diffusion, and relocation diffusion.

What is an example of air diffusion? ›

1. You can smell perfume because it diffuses into the air and makes its way into your nose. 2. Cigarette smoke diffuses into the air.

What is an example of liquid diffusion? ›

Diffusion of gas in liquid has an example of oxygen dissolved in water. Example of liquid diffusion in liquid is alcohol dissolved in water.

What are the 4 types of diffusion? ›

There are six types of cultural diffusion:
  • Relocation Diffusion.
  • Expansion Diffusion.
  • Contagious Diffusion.
  • Hierarchical Diffusion.
  • Stimulus Diffusion.
  • Maladaptive Diffusion.
23 Feb 2021

Is coffee an example of diffusion? ›

Whenever you smell the lovely smell of fresh coffee or drop a tea bag into hot water you're benefiting from diffusion: the fact that particles moving at random under the influence of thermal energy spread themselves around.

Is Sweating an example of diffusion? ›

When our body temperature rises, we sweat. This is a response to the excess heat and the evaporation of sweat results in the cooling of the body. This allows the heat molecules to dissipate and our body temperature to lessen. So, excess heat from the body diffuses away in the form of evaporation of sweat.

What is an example of direct diffusion? ›

An example of direct diffusion is between the United States and Canada, where the people living on the border of these two countries engage in hockey, which started in Canada, and baseball, which is popular in American culture.

What are 2 examples of stimulus diffusion? ›

Stimulus Diffusion

The McDonalds fast food chain originating in the US midwest having developed different menu items in different regions of the world. The changing interpretations of religious texts as they are translated into other languages.

What is an example of expansion diffusion? ›

Answer and Explanation: One example of expansion diffusion is the spread of viral videos from one location to others through contagious diffusion. The videos, such as the Kiki Challenge or Harlem Shake, spread from one person to another.

What is osmosis example? ›

Examples of Osmosis

The absorption of water from the soil is due to osmosis. The plant roots have a higher concentration than the soil. Therefore, the water flows into the roots. The guard cells of the plants are also affected by osmosis.

What are the 3 types of osmosis? ›

The three types of osmotic solutions are Isotonic, Hypertonic, and Hypotonic. The solute concentration is equal on both sides of cells in isotonic solution. An isotonic solution is ideal for animal cells.

What are the 3 types of transport? ›

The different modes of transport are air, water, and land transport, which includes rails or railways, road and off-road transport. Other modes also exist, including pipelines, cable transport, and space transport.

Is tea an example of diffusion? ›

As the water is added to the teabag it causes the tea leaves to move and triggers diffusion of the leaves. Diffusion is defined as the movement of a substance from an area of higher concentration to an area of lower concentration. There are lots of tea molecules in the bag and none outside.

Is smoke an example of diffusion? ›

Smoke filling up a room is an example of diffusion. Diffusion occurs when particles move from relatively high concentration to relatively low concentration. When smoke is released into a room, it spreads out.

How is soda diffusion? ›

Soda. Sodas go flat through diffusion. Air has a lower concentration of that bubbly carbon dioxide than the drink does, so the CO2 molecules depart the beverage and spread into the air.

Is Steam an example of diffusion? ›

Water Vapor & Evaporation

Vapor is really diffused water molecules that appear as fog or mist. When water is heated, the molecules in the water vibrate and some of them escape into the air, thus becoming water vapor, or the gaseous state of water.

What is gas diffusion? ›

Gas diffusion involves random molecular movement from areas of high partial pressure to areas of low partial pressure. The rate of diffusion depends on the partial pressure (or tension) difference between each area.

What is the diffusion of solid? ›

Diffusion can take place in gases, liquids, or solids. In solids, particularly, diffusion occurs due to thermally-activated random motion of atoms - unless the material is at absolute zero temperature (zero Kelvin), individual atoms keep vibrating and eventually move within the material.

What are the 3 factors of diffusion? ›

Several factors affect the rate of diffusion of a solute including the mass of the solute, the temperature of the environment, the solvent density, and the distance traveled.

What is Key Stage 3 diffusion? ›

Key points

Diffusion is the movement of particles from higher to lower concentrations. Diffusion happens naturally and so does not require energy. Substances like oxygen, carbon dioxide and glucose move in and out of cells by diffusion.

What is an example of diffusion at home? ›

A drop of food coloring diffuses throughout the water in a glass so that, eventually, the entire glass will be colored. When steeping a cup of tea, molecules from the tea cross from the tea bag and diffuse throughout the cup of water.

What is an example of diffusion in biology? ›

Examples of diffusion in living organisms

Oxygen and carbon dioxide, dissolved in water, are exchanged by diffusion in the lungs: oxygen moves down a concentration gradient from the air in the alveoli to the blood. carbon dioxide moves down a concentration gradient from the blood to the air in the alveoli.

Is facilitated diffusion an example of passive transport? ›

Facilitated transport is a type of passive transport. Unlike simple diffusion where materials pass through a membrane without the help of proteins, in facilitated transport, also called facilitated diffusion, materials diffuse across the plasma membrane with the help of membrane proteins.

What 3 factors can make diffusion faster? ›

The greater the difference in concentration, the quicker the rate of diffusion. The higher the temperature, the more kinetic energy the particles will have, so they will move and mix more quickly. The greater the surface area, the faster the rate of diffusion.

What are three characteristics of simple diffusion? ›

The characteristics of simple diffusion are concentration gradient, particle or molecule size, and permeability of the membrane.

What is diffusion 7th grade? ›


How does diffusion work Grade 8? ›

As they move, particles tend to spread out. If there is a large concentration of one type of particle in an area, they will tend to move away from that area. This movement of particles, from an area of high concentration to an area of low concentration, is called diffusion.

What is plant diffusion? ›

“Diffusion is the process of movement of molecules from a region of higher concentration to a region of lower concentration.” Diffusion in Plants. Diffusion is a very important process for photosynthesis where carbon dioxide from the stomata diffuses into the leaves and finally into the cells.

Is tea an example of diffusion? ›

As the water is added to the teabag it causes the tea leaves to move and triggers diffusion of the leaves. Diffusion is defined as the movement of a substance from an area of higher concentration to an area of lower concentration. There are lots of tea molecules in the bag and none outside.

What is an example of direct diffusion? ›

An example of direct diffusion is between the United States and Canada, where the people living on the border of these two countries engage in hockey, which started in Canada, and baseball, which is popular in American culture.

Is coffee an example of diffusion? ›

Whenever you smell the lovely smell of fresh coffee or drop a tea bag into hot water you're benefiting from diffusion: the fact that particles moving at random under the influence of thermal energy spread themselves around.


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