Question

[jackinthepatch]

Explain why cells can be stored for long periods of time in liquid nitrogen at very low temperatures but not in a freezer?

I sort of have an answer...but I'm not real sure on it, so any help would be appreciated.

Thanks guys.

[shonakennedy]

water expands when it freezes. which would in turn kill the cell. nitrogen doesnt.

[jackinthepatch]

Simple as that? Ok thanks lol (Y)

[shonakennedy]

lol well from the top of my head that is the simplest explanation. id totally try to confirm it for you but im at work and all my biol stuff from 2 years ago is back at home.

i mean cells are made up of water... and im sure im not the only one to have put a bottle full of water full to the brim into the freezer. when water solidifies it creates bonds that are further appart (i cant remember what type... or if thats completelly correct.. but im sure it is) and with the bonds pushing the cells further away, it causes the H2O to expand... which would damage a cell. where as nitrogen like snap freezes it and skips the whole process of expansion...

[jackinthepatch]

Actually, it doesn't have anything to do with the fact that water forms crystals upon freezing, which are 'sharp' and can therefore destroy cell membranes, does it? Because this would lead to cells being destroyed when defrosted...
And if liquid nitrogen is used, no crystals are formed, therefore no damage to membranes...?
Maybe a plausible answer? Yes/no? Lol.

[cns1511]

Actually, it doesn't have anything to do with the fact that water forms crystals upon freezing, which are 'sharp' and can therefore destroy cell membranes, does it? Because this would lead to cells being destroyed when defrosted...
And if liquid nitrogen is used, no crystals are formed, therefore no damage to membranes...?
Maybe a plausible answer? Yes/no? Lol.

That would be a plausible answer. The expanding of water upon freezing is similar to the sharp crystals formed so either could be used for this question.

[jackinthepatch]

Oh cool thanks mate

[hard]

what chapter's this in? is that a q of chapter 1 regarding the features of water molecules?

[jackinthepatch]

Ohh naa it was an 'extension' question on a practice SAC we had to do. Wasn't really necessary to answer it, but I figured I'd try and make myself look like a hard worker haha.