Fick's Laws of Diffusion
Physical laws describing solute diffusion mass transport across biological concentration gradients.
Governing formula
1st: J = -D (dC / dx); 2nd: ∂C / ∂t = D (∂²C / ∂x²)
SI unit
mol/(m²·s) (Flux J) & m²/s (Diffusion Coefficient D)
In depth
Fick's First Law relates diffusive mass flux J directly to concentration gradient dC/dx. Fick's Second Law describes time-dependent concentration changes over distance.
Examples in the real world
Calculating oxygen gas diffusion rates across lung alveolar-capillary membrane membranes.