Factors Affecting Diffusion Rate

1. Temperature

• Key Influence: Higher temperature increases the diffusion rate.
• Example:
  • Two situations:
    • At 5°C
    • At 30°C
  • Particles move from higher to lower concentration in both.
  • Faster diffusion at 30°C due to increased kinetic energy of particles.

2. Concentration Gradient

• Definition: Difference in concentration between two areas.
• Examples:
  • Situation A: 6 particles on the left, 2 on the right.
  • Situation B: 12 particles on the left, 2 on the right.
  • Analysis:
    • Steeper gradient in B (difference of 10 particles) than in A (difference of 4 particles).
    • Steeper concentration gradient results in a higher diffusion rate.
• Application:
  • Biological Example:
    • Alveoli in lungs: Higher oxygen concentration in alveoli than in capillary allows for oxygen to diffuse into the blood.
    • Breathing in more air increases alveolar oxygen concentration, steepens the gradient, enhancing oxygen diffusion.
  • Future Study:
    • Relevance in plant transport and transpiration (Chapter 7).

3. Surface Area

• Concept: Increased surface area enhances diffusion rate.
• Example:
  • Two animal cells:
    • Cell without microvilli.
    • Cell with microvilli.
  • Microvilli Function:
    • Increases the surface area of the cell membrane.
    • Allows more particles to enter the cell simultaneously.
• Effect: Enhances space for particles to enter the cell, increasing diffusion rate without changing cell size.