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Diffusion is a fundamental process by which particles spread from an area of higher concentration to an area of lower concentration. It is driven by the random motion of particles and continues until there is an equal distribution of particles throughout the system.

Basic Principles of Diffusion

1. Random Motion of Particles:

   • Particles (atoms, molecules, ions) are in constant, random motion due to their kinetic energy.

2. Concentration Gradient:

   • Diffusion occurs down a concentration gradient, meaning particles move from regions of high concentration to regions of low concentration.

3. Equilibrium:

   • The process continues until the concentration of particles is uniform throughout, reaching a state of equilibrium.

Factors Affecting Diffusion

1. Temperature:

   • Higher temperatures increase the kinetic energy of particles, leading to faster diffusion rates.

2. Concentration Gradient:

   • A steeper concentration gradient results in a higher rate of diffusion.

3. Medium of Diffusion:

   • Diffusion occurs faster in gases, slower in liquids, and slower in solids due to differences in particle mobility.

4. Particle Size:

   • Smaller particles diffuse faster than larger particles.

5. Viscosity of the Medium:

   • Higher viscosity (thickness) of the medium slows down diffusion.

6. Distance:

   • The greater the distance the particles need to travel, the slower the diffusion process.

Types of Diffusion

1. Simple Diffusion:

   • Movement of particles directly through a membrane or medium without the assistance of transport proteins or energy input.

   • Examples: Oxygen and carbon dioxide diffusing across cell membranes.

2. Facilitated Diffusion:

   • Movement of particles across a membrane through specific transport proteins.

   • No energy input is required, still moves down the concentration gradient.

   • Examples: Glucose and amino acids transported into cells via carrier proteins.

3. Osmosis:

   • A special case of diffusion is where water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.

   • Essential for maintaining cell turgor pressure and regulating cell volume.

4. Dialysis:

   • Diffusion of solutes across a semi-permeable membrane.

   • Used in medical treatments like kidney dialysis to remove waste products from the blood.