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==Introduction==
==Introduction==
==Ficks Law==
==Ficks Law==
[[Image:simpdifdiag.jpg|right|thumb|250px|<small><center>A Simple Schematic Diagram of Diffusion Across a Cell Membrane(Courtesy of Mariana Ruiz Villarreal)</center></small>]]
[[Image:simpdifdiag.jpg|right|thumb|250px|<small><center>A Simple Schematic Diagram of Diffusion Across a Cell Membrane(Courtesy of Mariana Ruiz Villarreal)</center></small>]]
<big>'''Q = DA((C<sub>1</sub> - C<sub>2</sub>) ÷ L)'''</big>
'''Q''' = the transport rate of a substance by diffusion
'''D''' = The diffusion coefficient
'''A''' = The cross sectional area which the substance is to diffuse across
'''C<sub>1</sub> C<sub>2</sub>''' = The concentrations in the two areas
'''L''' = distance separating the two areas
Ficks law demonstrates that the rate of diffusion can be maximised by increasing the area over which diffusion can occur, minimising the distance it has to occur over and increasing the gradient it occurs along. In the body it tends to be the former two which are taken into account when adapting surfaces for diffusion to occur over.
Ficks law demonstrates that the rate of diffusion can be maximised by increasing the area over which diffusion can occur, minimising the distance it has to occur over and increasing the gradient it occurs along. In the body it tends to be the former two which are taken into account when adapting surfaces for diffusion to occur over.
==Diffusion Through the Lipid Bilayer==
==Diffusion Through the Lipid Bilayer==
* Lipid soluble substances are able to diffuse freely across the lipid bilayer of cells.
* Lipid soluble substances are able to diffuse freely across the [[Phospholipid Bilayer - Anatomy & Physiology|lipid bilayer of cells.]]
* This obviously occurs passively down the concentration gradient.
* This occurs passively down the concentration gradient.
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[[Category:Transport Across Membranes]]