MadSci Network: Medicine

Re: What would happend if put blood cell in to distilled water, 0.9%saline .

Date: Wed May 21 09:04:17 2003
Posted By: Paul Odgren, Assistant Professor, Dept. of Cell Biology
Area of science: Medicine
ID: 1052849380.Me

Dear Ivan,

Thanks for your question. 

What happens has to do with a blood cell's membrane. There are tiny pumps 
made of protein in it whose job it is to try to balance the concentration 
of salt inside and outside the cell. The normal salt concentration in blood 
is about 0.9%, so if you put blood cells into that, they are just fine. But 
if you put them into water, they begin to pump water in to dilute their 
internal salt concentration to match that of the water. They swell up like 
little balloons until they burst and release the cells' contents. Not good. 

If you do the opposite, put them into very high salt, they pump water out 
and shrivel up. This property is taken advantage of in freezing blood for 
blood banks. The cells are protected from freezing by adding glycerol to 
them. When they are thawed out, the glycerol has to be removed before they 
can be transfused into a patient. This is done by adding high salt (6%), so 
the cells pump out the glycerol. The glycerol-containing liquid is removed 
and then the salt is reduced back down to 0.9% so they can be used safely. 

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