8 upvotes, 2 direct replies (showing 2)
View submission: Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology
Freezing slows biological processes but does not stop them. Sample degradation will continue happening at low temperatures just much slower. DNA is more stable than protein or RNA so it's often kept at -20C. Protein and RNA are often kept at -80C. Live cells are often kept at -180C.
In an ideal world everything would be kept at ultra low temperatures, but the lower the temperature, the more it costs to store. To get -180C requires liquid nitrogen which is a lot more expensive than running a compressor (IEA for -20 and -80 freezers)
Another benefit of storing samples at low temperatures is that fluctuations in temperature won't cause accidental thaws. If samples were kept at -5C, then opening the door might cause the temp to jump up past 0C causing a thaw then a refreeze which degrades samples much faster.
Comment by Mockingjay40 at 18/01/2024 at 21:18 UTC
2 upvotes, 1 direct replies
You can keep bacteria at -80 for a VERY long time without any real problems. Heck, Petri dishes can be stored for a couple weeks in the fridge
Comment by Bacontoad at 17/01/2024 at 23:38 UTC
1 upvotes, 1 direct replies
The slowing down but not stopping makes sense, but how did they discover the different temperature requirements in the first place? I mean I imagine with trial and error with something like yeast you could tell that either it's alive or it's dead by trying to proof it. But when it comes to something like say a butterfly cocoon or a frog egg, how well is it understood which processes will keep going and which will stop at precise temperatures? Do the chemical reactions all slow down at the same rate as the temperature decreases? Can one stop earlier and then everything else derails like a train? Sorry for all the follow-up questions. I guess I'm trying to picture something to my head that's really difficult for me to visualize. I'd appreciate any resources you could recommend, especially ones with visual models.