What is Diffusion? – Definition, Type & Examples | Biologyideas.com

What is diffusion?

Diffuse – to spread/ disperse/flow out or move in all directions.

Diffusion Definition Biology – Diffusion is the movement of particles (Ions, atoms or molecules) of different substances (solid, liquid and gases) from a region of higher concentration to a region of lower concentration due to their inherent kinetic energy till they get distributed uniformly and a dynamic equilibrium is attained.

Diffusion is a method of passive transport.

In plant diffusion Passive transport is a phenomenon which occurs naturally and doesn’t require expenditure of energy.

In passive transport, the substances move from a region of higher concentration to a region of lower concentration till they get uniformly distributed.

Mechanism of Diffusion

• Diffusion Pressure (DP) – The pressure exerted by the diffusing particles is known as Diffusion Pressure.
• Diffusion Pressure is directly proportional to the number/concentration of diffusing particles.
• Diffusion is the net movement of molecules from a region of their greater diffusion pressure to the region of lower diffusion pressure.
• Principal of Independent Diffusion – The direction of diffusion of one substance is independent of the movement of another substance and depends upon the difference in diffusion pressure.
• Oxygen (O2) moves and Carbon Dioxide (C02) moves out from the stomata simultaneously during respiration.

Factors Affecting Diffusion

• Density
• Temperature
• Diffusion Pressure Gradient
• Diffusing Medium

Density

1. Larger molecules diffuse slowly compared to smaller molecules.
2. Graham’s law of diffusion – Rate of diffusion of a gas is inversely proportional to the square root of its density.
3. Gas having higher density will move slowly compared to the gas with lower density.

Temperature

1. Increase in temperature increases the rate of diffusion because the kinetic energy increases.

Diffusion Pressure Gradient

1. Higher the diffusion pressure more rapid is the rate of diffusion.
2. Diffusion Pressure Gradient is directly proportional to diffusion pressure and inversely proportional to the distance.

Diffusing Medium

1. Higher the concentration of the diffusing medium lower is the rate of diffusion.
2. Diffusion is faster in vacuum and slower in air.

Importance of Diffusion

• Exchange of gases – Carbon dioxide enters the leaves through the stomata because the concentration of carbon dioxide is higher outside the leaves as compared to the air spaces within the leaves.
• Similarly, oxygen given off during photosynthesis diffuses out of the leaf air spaces through the stomata as the concentration of oxygen is comparatively lower outside the leaves.
• Transpiration occurs due to diffusion.
• Fragrance of flowers spreads to large distances through diffusion of volatile aromatic compounds and attracts pollinators (e.g. Insects).
• The substances get uniformly distributed within the cell cytoplasm through diffusion.

FAQs on Diffusion in Biology

References and Sources

• https://byjus.com/biology/diffusion/
• https://en.wikipedia.org/wiki/Diffusion
• https://www.merriam-webster.com/dictionary/diffusion
• https://www.thoughtco.com/what-is-diffusion-3967439
• https://biologydictionary.net/diffusion/
• https://www.jotscroll.com/what-is-diffusion-in-biology-definition-diffusion-examples

Further Readings

1. Plant Water Relation
2. Greenhouse Technology
3. Greenhouse Technology – Advantages and Applications
4. Imbibition
5. Osmosis
6. Meristematic Tissue System
7. Fruit
8. Leaves
9. Modification in Leaves
10. Epidermal Tissue System