Diffusive Constant

$D=\frac{{\delta }^2}{2\tau }$

• Diffusive constant
• Essentially tells you how quickly something diffuses
• $\tau$ is the time per step
• Has units of $\frac{{\mathrm{m}}^2}{\mathrm{s}}$

Molecule	$D$ in $\mathrm{H}{}_2\mathrm{O}$ at $25^{\circ }\mathrm{C}(\mathrm{c}{\mathrm{m}}^2/s)$
$\mathrm{CO}{}_2$	$1.9\cdot 10^{-5}$
$\mathrm{O}{}_2$	$2.1\cdot 10^{-5}$
Protein	$10^{-6}$
Protein in lipid	$10^{-8}$
Protein in cell	$10^{-7}$