Cambridge O Level Biology · Syllabus 5090 · Movement Into and Out of Cells
Rate of Diffusion
What is Rate of Diffusion?
The rate of diffusion is how quickly the net movement of particles down a concentration gradient occurs. Four factors raise it: a larger surface area, a higher temperature, a steeper concentration gradient and a shorter diffusion distance. Each acts through the random movement of the particles themselves, so none of them involves energy supplied by the cell. Real exchange surfaces such as alveoli, villi and root hair cells are adapted to maximise all four.
This definition is part of the Movement Into and Out of Cells chapter in Cambridge O Level Biology.
Last reviewed Syllabus 2026-2028