A Conversation for Osmosis

I'm confused.

Post 1


I'm confused. You've pretty much said what I thought all along, but last year we were told that semi-permiable membranes only prevent the flow of large solutes (proteins, carbohydrates, etc) and that small ions (eg. in KMnO4) can pass straight through (they are too small to be stopped). We even proved it by sticking some purple (KMnO4) in a piece of dialysis tubing and watching it diffuse out into the beaker of water we put it in.

But then what you said about dehydrating cells by placing them in a salt solution (which btw I know is correct) wouldn't work - the salt would just diffuse out...

They were using Dialysis tubing as the membrane, mabey that is different from cell membranes.... Yeah, I'm sure cell membranes are impermiable to ions... They have to have ion gates if they want ion flow across the membrane. Mabey I'm just getting confused between Dialysis tubing and cell membranes.

Anyway, good article!

I'm confused.

Post 2

Dr Hell

I think your problem with that is that you are thinking of a very special type of membrane. As I explained in the text any semi-permeable membrane you can think of will work.


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