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Simple Diffusion

What is Simple Diffusion

Simple diffusion is defined as the movement of substances like ions, atoms, and molecules from an area of their higher concentration to lower concentration without the involvement of any other molecules.

Simple Diffusion

How does Simple Diffusion Work and What happens during the Process

It occurs because the particles undergoing this process are always in a state of random motion. It is a natural phenomenon where the particles move along a concentration gradient in a solution or across a semipermeable membrane to attain a state of equilibrium on both sides.

What are the Characteristics of Simple Diffusion

  • Occurs across a semipermeable membrane
  • Requires a concentration gradient across the cell membrane
  • It is a passive transport mechanism thus require no energy expenditure
  • Does not need a carrier transport protein
  • Happens by random motion
  • Carried out by the actions of hydrogen bonds formed between water molecules and the solutes particles
  • Cannot be inhibited by an inhibitor molecule
  • It is non-specific to any particle
  • A comparably slow processthan other forms of diffusion

Practical Examples of Simple Diffusion

  • Gas exchangein plants with the help of stomata
  • Cellular respiration in animals where they breath in oxygen inside the bodyand send carbon dioxide out
  • The process by which animals including humans get rid of their waste products in the form of urea
  • The process by which small, uncharged, and lipid-soluble moleculespass between the phospholipid bilayer of the semipermeable membrane of the cells
  • Absorption of nutrients such as carbohydrates, minerals, and vitaminsin the small intestine
  • Delivering oxygen, water and small nutrients inside the cell of simple organism like amoeba and bacteria


Q1. Is simple diffusion active or passive transport?

Ans. Simple diffusion is a passive transport mechanism because it does not require energy expenditure by the cell.

Q2. How is simple diffusion different from active transport?

Ans.Simple diffusion move substances down its concentration gradientwithout the involvement of any other molecule and energy expenditurewhereas active transport helps in the transport of molecules against the concentration gradient assisted by other protein molecules and requiring energy expenditure by the cell.

Q3. How is simple diffusion different from osmosis?

Ans. Simple diffusion is the movement of particles from an area of their higher to lower concentration whereas diffusion involves the movement of water molecules from the area of less solute concentration to an area of high solute concentration.

Article was last reviewed on Wednesday, February 26, 2020

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