Biology Question

[Ameya Jalihal]

Hey people!
Its been long since anyone last posted questions here. I was wondering if the world has run out of questions... Haha.
I was reading up something about membranes when it struck me, I do not understand how diffusion works!
So here is my question which I thought some of you would find interesting:
How do water molecules pass through the lipid bilayer by "simple diffusion"? That first begs the question, what is simple diffusion anyway?
How do the molecules cross the hydrophobic center region? I do not find certain arguments about the size of water molecules convincing.
I hope my sketch explains my question.
                                 
                                                                              Membrane
                                h2o  h2o h2o        0========|  |=======0
                                                                0========|  | ======0   ----->h2o
                                      h2o                  0========|  |=======0         lumen
                                            h2o            0========|  |========0
 extra cellular space                               ^                 ^---------
    (outside the membrane)       Hydrophilic ends        Hydrophobic region (should virtually be a forbidden band equivalent for polar molecule, yes?)

Well i guess this is more of a physics question than anything..

Let me know if you find out anything!
Thanks.



                                       
--

Ameya Jalihal

[Sriram Chandramouli]

Even I stumbled across the same situation when I studied Molecular Biology and Cell Biology.. The only answer I got was that even though water is polar, in comparison to other molecules diffusing through the bilayered membrane its size is pretty small. 
I hope there is a stronger reason for that !
Will let you know when I found out..

--
In knowledge there is only Mathematics. All the rest is stamp collecting. ( I know it is supposed to be Physics, but who cares ? )

[Ameya Jalihal]

Thanks!

--

.................*A*meya *J*alihal