Table of Contents

• Prequiz...
• Just Plain Movement
• 1: Measuring Movement
• 2: Directed vs. Undirected Movement
• 3: Measuring Movement Using Flux
• Introducing Gradients
• 4: What is a gradient?
• 5: Watching diffusion happen (applet)
• 6: Visualizing the Gradient
• Fick's Laws, Part I
• 7: Fick's First Law
• 8: The gradient in Fick's First Law
• 9: A familiar equation for Fick's first law
• 10: The diffusion coefficient is the slope
• 11: What are the units for D?
• 12: How does flux depend on distance?
• 13: A fragrant example
• 14: General Transport Equations and Fick's First Law
• Fick's Laws, Part II
• 15: Fick's Second Law ...
• 16: ... is about "time to diffuse"
• 17: A Very Useful Formula
• 18: Time-to-diffuse "explodes"
• 19: General Functions and Diffusion
• Biological Applications
• 20: Biological Applications
• 21: Why do rhinos have lungs and amoebas don't?
• 22: Diffusion is efficient in small organisms, but not big ones
• 23: Diffusion within lungs
• 24: How many macrophages does it take to kill a virus?
• 25: You need a lot of macrophages - or one smart one!
• Review
• 26: Final Review

Fick's First Law

So now you know this Incredibly Important Concept:

Flux is directly proportional
to the steepness of the gradient.

This concept is known as Fick's First Law. In this section, I will introduce a mathematical version of this law and explore some of the things that we can learn by expressing this law mathematically.

Oh, and that is Adolf Fick. -->