osmolarity and diffusion question

[stubbs]

Hey

This is my first post so i'm not sure if this is the appropriate section to ask this question so please let me know if not.

Basically i'm studying medicine and specifically the kidneys currently and have managed to forget lots of my basic school bio knowledge so was hoping someone could help me out.

My question is this:

what happens if you have a membrane separating 2 solutions of different osmolarities and the membrane is only permeable to solute "X" (not even water).

if... solute X is in high concentration on one side relative to the other BUT the osmolarity of the solution on the other side is higher, what happens?

Any help is much appreciated.

[vampares]

If the membrane is permeable only to "X", osmolarity is irrelevant or the term is inappropriately applied here. The osmosis of "X" will be pressure dependent. If pressures are equal nothing will happen outside of some tainting due to Van der Waals force. X is not water, so the water on the other side of the membrane will become more diluted if X crosses the membrane. This would ultimately result in edema or perhaps dehydration depending on what X is.

Edited April 21, 2013 by vampares

[Leison]

Here osmolarity , osmolality , osmotic pressure is zero. As these term is used only if the membrane is permeable.

 

So a simple diffusion takes place...to balance x in both sides...

 

N this doesnt happen in human body...as every normal human body/ membranes are permeable to water.

So, no, edema n dehydration n no such event which requires water movement will take place...

 

 

One such compound that diffuses readily towards both memebranes is Urea in human body, thats y we dnt count urea while calculating osmolality, but yes we do need urea to calculate osmolarity.