Diffusion Lecture Notes

Introduction to Diffusion

• Definition: Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
• Concept: Molecules move randomly, spreading out from areas where they are concentrated to areas where they are less concentrated.
• Net Movement: Refers to the overall movement of particles as a group, despite individual particles moving randomly.
• Media: Diffusion can occur in both gases and liquids.
  • Example: Perfume spreading in a room or food coloring in water.

Diffusion Across Cell Membranes

• Cell Membranes: Act as barriers that are partially permeable.
  • Partially Permeable: Allows only certain small molecules to pass through.
  • Examples of Small Molecules: Water, glucose, amino acids.
  • Large Molecules: Proteins and starch cannot diffuse through because of their size.
• Passive Process: Diffusion does not require energy from the cell; it is driven by random particle movement.

Factors Affecting the Rate of Diffusion

1. Concentration Gradient

   • Difference in concentration between two areas.
   • Greater concentration gradient results in a higher rate of diffusion.
   • Example: Faster diffusion in a scenario with a stark contrast in particle concentration across areas.

2. Temperature

   • Higher temperatures increase particle energy and movement speed.
   • Results in a higher diffusion rate.

3. Surface Area

   • Larger surface area allows more particles to diffuse at once.
   • Leads to a higher diffusion rate.

Conclusion

• Diffusion is a fundamental process in biological systems, relying on concentration gradients, temperature, and surface area to occur efficiently.
• Understanding these principles can help explain processes such as nutrient absorption and gas exchange in living organisms.