Factors Affecting the Rate of Diffusion

Edexcel AS-level BiologyGas ExchangeLesson 4 of 23

The rate at which a gas diffuses across an exchange surface depends on three main factors. They are summarised by Fick's law:

So the rate is:
• directly proportional to the surface area: doubling the area doubles the rate;
• directly proportional to the difference in concentration across the surface: a steeper gradient gives a faster rate;
• inversely proportional to the thickness of the exchange surface (the diffusion distance): doubling the thickness halves the rate.

More in Gas Exchange

• Gas Exchange in Small Organisms
• Surface Area to Volume Ratio
• Gas Exchange in Large Organisms
• Effective Gas Exchange Systems
• The Human Gas Exchange System
• Gas Exchange in the Alveoli
• Adaptations of the Human Gas Exchange System
• Breathing

All 23 lessons in Gas Exchange · All Edexcel AS-level Biology topics