Time to Diffuse

Learning Outcomes

After completing this module you should be able to:

  • Explain how the rate of movement of a substance is proportional to the distance squared (Fick’s Second Law).
  • Measure the time it takes for a substance to move from one area to another as a function of distance and the permeability of the medium.


1: Fick's second law: ... is about "time to diffuse"
2: A very useful formula
3: Time-to-diffuse increases dramatically
4: General functions and Diffusion
5: Biological applications
6: Why do rhinos have lungs and amoebas don't?
7: Diffusion is efficient in small organisms but not big ones
8: Why we have lungs
9: How many macrophages does it take to kill a virus?
10: You need a lot of macrophages - or one smart one!
11: Summary