Adaptations for Rapid Transport (AQA AS Biology)

• The rate at which diffusion (including both simple diffusion and facilitated diffusion) occurs across external and internal cell membranes varies
• Some cells are adapted for rapid transport (diffusion) of molecules across their internal or external membranes
• The rate of diffusion depends on several factors. These include:
  • Temperature
  • The surface area of the exchange surface
  • The concentration gradient across the exchange surface
  • The thickness of the exchange surface

Simple diffusion

The rate of simple diffusion depends on three main factors:

Facilitated Diffusion

The rate of facilitated diffusion depends on two main factors