Similarities between Diffusion and Osmosis

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What is Diffusion?

In the presence of a concentration gradient (difference between concentrations in a given environment), an impetuous movement of particles/solutes from a high concentration to a low concentration area (down the concentration gradient) is known as Diffusion.

The movement of particles/solutes in an event of diffusion is across (down) the concentration gradient. The concentration gradient differential will eventually be nullified as the process of diffusion is progresses. Gaseous phase and/or liquid phase molecules are usually associated with the process of diffusion.

Diffusion does not require a semipermeable membrane and can occur in any​​environment/medium​​(liquid​​as​​well​​as​​gaseous).

The importance of diffusion can be highlighted with some of the significant examples of biological processes such as; breathing, perspiration and in plants; photosynthesis.

Similarities between diffusion and osmosis

The significance of diffusion is to generate energy essential for the functioning of in these processes.

The best explanatory examples of diffusion includes;

coloring agents which diffuse when put in a container full of water or an air freshener when          sprayed, spread throughout the area.

Diffusion is usually dependent on physical parameters such as :


density of the solute particles


The main driving force in the process​​ of​​ diffusion​​ is​​ the​​ free ​​energy​​ of​​ the​​ diffusant​​molecules/particles.

Here are the types of Diffusion

Some​​ of​​ the ​​prominent​​ examples​​ of​​ diffusion​​ are​​ explained​​ below.

  • Surface​​ diffusion:​​Wetting​​ of​​ solute ​​when​​ dropped​​ on​​ a​​ liquid​​
  • Osmosis: Yes, osmosis is, in essence, a process of diffusion. The diffusion of solvent ​​through ​​a​​semipermeable ​​
  • Facilitated diffusion: Spontaneous passive transport of ions or molecules across a cell membrane (different because it happens outside the active phase of osmosis or intracellular ​​diffusion).
  • Reverse Diffusion: Movement of solutes from lower concentration to higher similar to forward osmosis. Reverse diffusion is related to a separation of solutes along with solvent/water.

Definition and Characteristics of Osmosis

An extemporaneous movement of water/solvent from a lower concentration solution to a higher concentration solution across a semipermeable membrane is known as Osmosis.

The movement of solvent in an event of osmosis is against (up) the concentration gradient. The presence of semipermeable membrane is the main requirement for the process of osmosis. Osmosis​​can ​​occur ​​only ​​in​​ liquid ​​environment.

Osmosis is distinctly observed in situations such as; extracellular medium with a lower solute concentration (higher solvent) compared to intracellular environment with a higher solute concentration​​(lower​​solvent).

Similarities between diffusion and osmosis-1

Nutrients supply and processes such as; excretion to excrete bodily waste products are mainly driven by the process of osmosis in animals/organisms. In botanical systems, the distinct role of osmosis is in the processes of water absorption from the soil as well as the transport of water and liquid essentials to the leafy parts of the plant. The ultimate outcome of osmosis is reduction in the concentration gradient differential (equalization of concentration across a semipermeable​​membrane/barrier.

The best representative example to understand the process of osmosis is,

​salt solution

Salt always draws water/solvent towards its direction when concentrated intra- or extracellularly in a cell. This explains a significant increase in thirst when you eat salty food.

Many biological processes are dependent on osmosis such as; maintenance of cellular functions. The process of osmosis is solely dependent on the environment across a semipermeable membrane in a biological system. ​

Osmosis plays a significant role in biological processes since the solvent is always water and the movement of water and other essential nutrients across ​​cell ​​membranes ​​is​​ of​​ great​​ significance​​ in​​living ​​systems.

Here are the types of Osmosis

Broadly, there are two main types of osmosis. The pressure differential that drives the process​​ of​​osmosis ​​is ​​termed​​ as​​ osmotic ​​pressure.

  • Reverse Osmosis: When a volumetric and/or atmospheric pressure drives the movement of higher solute particles across the semipermeable membrane, the process is usually termed as reverse osmosis. The water purification principle is based on a process of reverse osmosis when the amount of impurities are lower to effect a regular process of osmosis. Therefore, a process of reverse osmosis is usually utilized to get a purified water in specific operations such as; pharmaceuticals, ​​medical​​
  • Forward Osmosis: Opposite of reverse osmosis, forward osmosis effects a movement of solutes from lower concentration to a higher solute concentration. Forward ​​osmosis​​ is​​essentially ​​the​​ opposite​​ of​​ normal​​


  • In plants; while the process of osmosis is responsible for water absorption as well as absorption of other essential liquids, diffusion plays a significant role in movement of molecules in some of the essential plant processes such as photosynthesis. In essence, both diffusion and osmosis play distinct role in the generation of energy and other essential​ ​nutrients ​​for​​ normal​​ life​​ cycle ​​of ​​
  • Both ​​diffusion​​ and​​ osmosis ​​are​​ dependent​​ on ​​concentration ​​
  • Both ​​processes​​ do​​ not ​​require​​ energy​​ and​​ are​​ essential​​ passive ​​transport​​
  • Both ​​diffusion​​ and​​ osmosis ​​can ​​occur ​​in ​​living ​​as ​​well​​ as​​ non-living​​
  • Both​​processes​​ultimately​​result​​in​​an​​equalization​​of​​solution​​
  • In essence, both diffusion and osmosis work together to move water molecules/solvents​​from​​higher​​to​​lower​​
  • Both processes have potential applications in industrial as well as small scale applications.
  • Both​​processes​​can​​occur​​when​​substance/molecule​​is​​present​​in​​a​​liquid​​
  • Both diffusion and osmosis are essential in the movement of substances across cell membranes.
  • Osmosis and diffusion play a significant role in the maintenance of homeostasis in physiological​​



Diffusion Osmosis









Author: Rohit Mulik

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