Fick's Law of Diffusion Calculator
Fick's Law states that the rate of diffusion is directly proportional to the surface area and concentration gradient, and inversely proportional to the thickness of the exchange...
Formula first
Overview
This principle governs how substances like oxygen and carbon dioxide move across biological membranes in the lungs and capillaries. Maximizing surface area and minimizing membrane thickness are key physiological strategies to ensure efficient gas exchange. Understanding this law explains why respiratory distress occurs when the diffusion pathway is widened by fluid or scarring.
Symbols
Variables
Rate = Rate of diffusion, A = Surface Area, \Delta C = Concentration Gradient, T = Membrane Thickness
Apply it well
When To Use
When to use: Apply this when calculating or evaluating the efficiency of gas exchange across a biological barrier, such as the alveolar-capillary membrane.
Why it matters: It explains the fundamental limitations of gas exchange in the human body, dictating the design of lungs, gills, and capillary networks.
Avoid these traps
Common Mistakes
- Confusing inversely proportional by putting thickness in the numerator.
- Forgetting that the concentration gradient is the difference in concentration between the two sides of the membrane.
One free problem
Practice Problem
If the surface area for gas exchange is 50 m?, the concentration gradient is 2 mol/m?, and the membrane thickness is 0.05 m, what is the rate of diffusion assuming a constant of 1?
Solve for:
Hint: Divide the product of Area and Gradient by the Thickness.
The full worked solution stays in the interactive walkthrough.
References
Sources
- AQA A-Level Biology Specification / Guyton and Hall Textbook of Medical Physiology