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What is the Difference Between Osmosis and Diffusion?

Diffusion and osmosis are mostly used interchangeably by not only lay people but also some of the students who are pursuing science. There is a lot of difference between osmosis and diffusion.

Before getting right into the difference between osmosis and diffusion, we will discuss what osmosis and diffusion mean, their types, applications in our lives, etc. so that you can get a clearer picture of what osmosis and diffusion are.

Difference between osmosis and diffusion: Osmosis

By OpenStax, CC BY 4.0, Link

Osmosis can be defined as the movement of a solvent (liquid) from where it (solvent) is in higher concentration to where it is in lower concentration through a semi-permeable membrane.

The solvent is usually water. The semi-permeable membrane is permeable only to solvent but not solute.

Note: In a given solution, a solute is something which is present in lower concentration, and the solvent is the one which is present in higher concentration.

To make it further easy, the solvent moves from lower solute concentration to higher solute concentration to maintain the equilibrium or balance.

Osmosis plays a key role in biological systems as most of the biological membranes are semi-permeable.

Factors which influence osmosis

The distance of diffusion – Greater the distance, slower the osmosis.

Temperature – Higher the temperature, faster the osmosis.

Concentration gradient – The difference in the concentration between two solutions which are present on either side of the semi-permeable membrane. This is also called an osmotic gradient.

Osmotic pressure – It is the pressure on the solution which doesn’t allow the solvent to pass through the semi-permeable membrane. This pressure is usually normal so as to allow osmosis to happen.

Types of Osmosis

Forward osmosis – It is a process where osmotic pressure is used to separate water from the solute.

Reverse osmosis – It is a process where osmotic pressure is used to retain the solute on one side and move the solvent through a semi-permeable membrane completely from the given solution.

Reverse osmosis may look pretty much like how osmosis functions but if you remember, osmosis is the movement of solvent from lower solute concentration to higher solute concentration, but here in reverse osmosis, the solvent is forcibly moved from higher solute concentration to the lower solute concentration.

Uses of osmosis

It prevents cells from rupturing the plasma membrane.

It helps cells to maintain fluid balance and blood volume.

It helps in transfusion (a process of transferring blood or any other fluid from donor to recipient).

It causes tissue spaces to accumulate fluid.

Difference between osmosis and diffusion: Diffusion

It is the movement of particles from where they are in higher concentration to where they are in a lower concentration.

The movement of particles happens because the particles present in higher concentrations have free energy. So, they move from higher concentration to lower concentration.

Did you notice that we didn’t use words like a solution, solvent or solute? What did you understand by that?

The answer is simple. Unlike osmosis where movement takes place only in liquids, diffusion takes place in solids, liquids, and gases.

You might have noticed that we didn’t even talk about any semi-permeable membrane either. It is because a semi-permeable membrane is not required for diffusion to take place.

Factors influencing diffusion

Weight of molecules – Larger molecules will take more time to diffuse.

Concentration gradient – Higher the difference in concentration, faster the diffusion.

Pressure – Higher the pressure, slower the diffusion.

Temperature – Higher the temperature, faster the diffusion.

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Types of diffusion

There are several types of diffusion and these types are generally used in specific fields of studies and are not required by general Joes and Janes like us.

However, we are just noting down the different types of diffusion

Anomalous diffusion – It takes place in a porous medium

Anisotropic diffusion – It is also known as Perona-Malik diffusion

Atomic diffusion – It takes place in solids

Heat equation – Diffusion of thermal energy

Eddy diffusion – Diffusion of any particles due to eddies

Effusion – Diffusion of gas from small holes

Bohm diffusion – Diffusion of plasma across the magnetic fields

Electronic diffusion – The current produced in a semiconductor which is caused by the diffusion of charge carriers.

Facilitated diffusion – It is present in almost all organisms.

Gaseous diffusion – It is used to separate different isotopes of elements

Kinesis – Movement of cells in response to a stimulus

Reverse diffusion – Diffusion of particles against the concentration gradient

Molecular diffusion – Diffusion of molecules

Knudsen diffusion – Diffusion of gas in long holes with constant and frequent collisions with walls.

Itō diffusion

Lévy flight

Momentum diffusion

Random walk

Surface diffusion – Diffusion of particles on the surface.

Rotational diffusion – Reorientation of molecules randomly in a medium

Photon diffusion – Diffusion or travel of photons without being absorbed

Trans-cultural diffusion

Plasma diffusion

Turbulent diffusion – Diffusion of any material within a turbulent fluid

Note: The ones which are not described are either in the field of mathematics or physics (higher level).

Uses of diffusion

Passage of waste products in renal tubules happens via diffusion.

Gas exchange in the lungs and tissues occurs only and only through diffusion.

Some of the nutrients in the gastrointestinal tract are absorbed through diffusion only.

Difference between osmosis and diffusion

Now that we fully understood what is diffusion and what is osmosis, it is time for us to learn the differences between osmosis and diffusion.

Osmosis needs a semi-permeable membrane whereas diffusion doesn’t need any such membrane.

Osmosis can take place only in liquids and diffusion takes place in solids, liquids, and gases.

Osmosis is a slow process and diffusion is a fast process.

In osmosis, the movement of a solvent (liquid) is only seen and in diffusion, particles which move can be solids, liquids or gases.

The medium of osmosis is liquid and the medium of diffusion can be either solid, liquid or gas.

The concentration of the solvent does not become equal on both sides of the semi-permeable membrane whereas the concentration of diffused particles is equal in the given available space.

The movement of diffusion helps in equalizing energy whereas the movement of osmosis doesn’t serve this purpose.

Osmosis is opposed by turgor pressure and hydrostatic pressure whereas these pressures don’t usually apply to diffusion

Osmosis doesn’t deal with the transport of any nutrients but diffusion deals with transport of nutrients, minerals, etc.

Osmosis takes place in only the same solutions but diffusion takes place in both similar and different solids, liquids or gases.

The movement of particles is unilateral in osmosis whereas, in diffusion, the particles move in all directions.

Osmosis depends on solute potential but diffusion doesn’t depend on solute potential, water potential, or pressure potential.

However, there are few similarities like both osmosis and diffusion are passive processes and in both, the movement of particles takes place from higher concentration to lower concentration.

This ends our difference between osmosis and diffusion. We don’t think understanding it was that difficult or was it? Do comment below and let us know!

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