Diffusion vs. Osmosis

The difference between diffusion and osmosis can be narrated as, diffusion is the movement of molecules and atomsfrom an area of higher concentration to an area of low concentration while osmosisis a process by which molecules of a solvent (mostly water) pass through aselectively permeable membrane from an areahaving solute concentration less (high water potential) to an area ofhigh solute concentration( low water potential).

Advertisement - Continue Reading Below
Diffusion vs. Osmosis

It is to be noted that the presence of a semipermeable (selectively permeable membrane) is necessary for osmosis but not for the diffusion process. A membrane may or may not present at the place where the diffusion process is going on. Examples of semipermeable membranes are a membrane of the egg inside its shell, a peritoneal membrane inside human peritoneum cavity, the membrane of lungs and intestine.

Diffusion occurs where the molecules are in a continuous state of motion and that kinetic energy of motion tends molecules to move towards the low concentration gradient from a higher concentration gradient. While the driving force for osmosis is the difference in the free energy of the system on either side of the membrane due to the difference in solvent (mainly water)
potential.

Advertisement - Continue Reading Below

In diffusion, solute particles move from an area of high solution concentration to low solution concentration till the concentration of solution on both sides becomes equal.  While in osmosis the water particles move from an area of low solution concentration (where water potential is high) to a high solution concentration (where water potential is low).

Diffusion may occur in the molecules of liquid, gases or solids whereas osmosis occurs only in the molecules of liquids mainly water.

There are three types of diffusion. 1st is simple diffusion in which molecules simply move along the concentration gradient, 2nd is facilitated diffusion in which a carrier protein
is required for the transport of molecules and 3rd is osmosis. Thus simply saying, osmosis is a subtype of diffusion. Osmosis can be classified as exosmosis and endosmosis in which water molecules move outside of inside the membrane respectively.

Advertisement - Continue Reading Below

Diffusion is a fast process while osmosis is a slow process. In diffusion, movements of molecules are over a large distance while in osmosis , the movement is over a
short distance. Both diffusion and osmosis are passive movements, i.e. no energy are required for there movements. Osmosis of solvent or water occurs towards the
area where solute particles are not allowed to move. While in diffusion there is no this type of restriction.

Examples of diffusion process from common life can be given as the smell of perfume which diffuses out into the air and makes its way into the nose. A tea bag placed in a cup of water also
diffuses out in the water. Cigarette smoke diffuses out in the air. An example of osmosis from common life can be given as the water given to the plants enters
their roots , stalk and then reaches their leaves by osmosis.

When a cell is kept in a hypertonic environment, water comes out of the cell because of the higher concentration of solution outside. Conversely speaking, when the cell is kept in a hypotonic environment, it becomes swell because water enters the cell from outside and even may burst like a balloon. When a cell is kept in an isotonic environment, no change in the cell takes place because of equal concentration gradient outside and inside.

Comparison Chart.

BasisDiffusionOsmosis
DefinitionMovements of molecules from a high concentration gradient area to an area of a low concentration gradient.Movements of solvent(water) molecules across a semipermeable membrane from higher water potential to low water potential.
Presence of membrane Not necessary for diffusion.Necessary for osmosis.
Driving forceContinuous motion of molecules.The difference in free energy of system on either side of the membrane.
Movements between solutionsFrom the high concentration of the solution to low
concentration.
From low concentration of the solution to a high
concentration of the solution.
MediumMay occur in the molecules of solid, liquid or
gases.
Only occurs in the molecules of liquid mainly water.
SpeedIt is a fast process.It is a slow process.
Area requiredIt occurs along a wide area.It occurs along a short distance.
Types3 types of diffusion. Simple diffusion facilitated diffusion and osmosis.2 types of osmosis. Exosmosis and endosmosis.
Examples1.Perfume spread in the air.
2. Tea bag in a cup of water diffuses out.
Water reaches from the root of the plant to the leaves.
Advertisement - Continue Reading Below

What is Diffusion?

Diffusion is actually the motion of atoms or molecules from an area of higher concentration gradient to an area of a lower concentration gradient. It can occur in the molecules of liquid, gases or solids. The actual driving force for diffusion is the free motion of molecules which produce energy and the process of diffusion starts and continues till the concentration of both solutions become equal.

Biological Significance of diffusion.

The biological significance of diffusion is that the fluid inside the cell has a higher concentration of potassium and low concentration of sodium. While the extracellular fluid has a higher concentration of sodium and low concentration of potassium. Both sodium and potassium move freely across the cell membrane. If this movement of sodium and potassium across the cell membrane do not occur , life cannot exist.

What is Osmosis?

Osmosis is a phenomenon by which the molecules of a solvent mainly water moves from an area of low solution concentration to higher solution concentration (High solvent concentration to lower solvent concentration) through a selectively permeable membrane. Osmosis occurs only in the molecules of liquid mainly water. The driving force for osmosis is the difference in free energy on either side of the membrane. There are 2 types of osmosis. Exosmosis and endosmosis, i.e. when solvent molecules move outside or inside the membrane respectively.

Advertisement - Continue Reading Below

Biological Significance of Osmosis.

The biological significance of osmosis is that the cell contains many proteins inside it which cannot move across the cell membrane. These proteins include albumin, globulins and many others.
Although waters move by osmosis across the semipermeable membrane, these largely sized proteins cannot move due to their size and retained within the cell and
perform their  function here. If the cell loses its proteins, life may not be possible.

Examples from the human body.

The process of diffusion occurs at many places in the human body. Diffusion of oxygen from the alveolar spaces in the lungs to blood is essential for survival. Similarly, carbon dioxide diffuses
out from the blood into lungs and removed by lungs. Diffusion of water, salts and waste products occur in the kidney. Digested particles of food diffuse in the colon.

Osmosis occurs both in the small and large intestines mainly in the large intestine. Important nutrients are absorbed via osmosis from the large intestine.

Key Differences between Diffusion and Osmosis

  1. Diffusion is actually the motion of molecules or atoms from an area of high concentration  to an area of less concentration gradient while osmosis is the  motion of molecules
    of water across a semi-permeable membrane from high solvent to lower solvent concentration.
  2. Semi-permeable membrane is mandatory for osmosis while not necessary for diffusion.
  3. Diffusion is a fast process while osmosis is a slow process. A large area is required for diffusion while the small area is required for osmosis.
  4. Driving force for diffusion is the continuous motion of the molecules while that of osmosis is the difference in energy across the membrane.
  5. Diffusion occurs in the molecules of solids, liquids or gases while osmosis occurs only in the molecules of liquids.

Conclusion

In the above article, we see the clear difference between diffusion and osmosis. Diffusion and Osmosis are vital processes which occur in our body , in plants, animals and in our surroundings all the time and it is essential to gain knowledge about these processes.

Advertisement - Continue Reading Below

Leave a Comment