Overview
This lecture explains the main factors that influence the rate of diffusion, including temperature, concentration gradient, and surface area, with relevant biological examples.
Factors Affecting Diffusion Rate
Temperature
- Higher temperature increases the kinetic energy of particles, leading to a higher rate of diffusion.
- Diffusion occurs faster at 30°C compared to 5°C due to increased particle movement.
Concentration Gradient
- Concentration gradient is the difference in concentration between two areas.
- A steeper concentration gradient (e.g., 12 vs 2 particles) increases the rate of diffusion compared to a less steep gradient (e.g., 6 vs 2).
- Particles move from regions of higher to lower concentration, resulting in more frequent collisions and faster diffusion when the gradient is steep.
Application: Gas Exchange in Lungs
- Oxygen diffuses from the alveoli (higher concentration) into the blood (lower concentration).
- Breathing in more air increases alveolar oxygen concentration, steepening the gradient and raising the diffusion rate of oxygen into the blood.
Surface Area
- Greater surface area allows more particles to diffuse at once.
- Cells use structures like microvilli to increase membrane surface area, enabling more efficient diffusion without changing cell size.
Key Terms & Definitions
- Diffusion — The movement of particles from an area of higher concentration to an area of lower concentration.
- Concentration Gradient — The difference in concentration between two regions.
- Kinetic Energy — The energy that particles have due to their motion.
- Microvilli — Cell membrane folds that increase surface area for absorption or diffusion.
Action Items / Next Steps
- Review upcoming chapters on plant transport and transpiration for more examples of diffusion and concentration gradients.
- Be prepared to apply these diffusion concepts to biological systems like the lungs and plant cells.