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I'm wondering what effects are known to happen to a person's cells when a person is cryogenically frozen, especially those that need to be overcome in order to "bring them back to life."

From a cellular and maybe even molecular level, is the person exactly the same as before?

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closed as primarily opinion-based by Chris, anongoodnurse, The Last Word, WYSIWYG, Bez Jan 17 '15 at 11:52

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ It's not possible to freeze a person and bring it back to life later. $\endgroup$ – Chris Jan 16 '15 at 22:03
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    $\begingroup$ Possible or not, I'm still curious what effects have been observed - the study of Cryonics still seems to active. $\endgroup$ – DoubleDouble Jan 16 '15 at 22:08
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    $\begingroup$ @Chris wrong! Well, maybe. Check out this frog $\endgroup$ – tel Jan 16 '15 at 23:36
  • $\begingroup$ You need to add details or stick to one domain- molecular/physiological. In any case since this has not been done on humans the answer can be based only on speculations. $\endgroup$ – WYSIWYG Jan 17 '15 at 8:56
  • $\begingroup$ @tel: More to point, we know that it is possible to freeze human sperm for later re-use. That leads me to wonder if we can someday freeze human BEINGS for re-use. After all,who would have ever guessed that we could clone sheep. $\endgroup$ – Tom Au Feb 16 '15 at 23:03
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Short Answer

Death!

Longer Explanation

In terms of the cellular and molecular level, many of the relatively weak interactions holding a person together are disrupted by cold temperatures. As a cell freezes, most of its proteins and lipid membrane content will denature and "fall apart", the same as if you boiled it.

As with many things in biology, the problem is water. At room temperature, the lipid bilayers and proteins of a cell are held together largely by way of a complex network of interactions with the surrounding water. If the cell gets too hot or too cold this network of interactions between biomolecules and water falls apart. This leads to a disruption of the cell's overall organization*, which in turn can cause problems up to and including complete cell rupture and death.

So in order to preserve a living creature under cryonic conditions you need to replace the water in and around its cells with a different molecule that will maintain most of the normal intermolecular interactions even under conditions of extreme cold. There are protocols for freezing cell cultures that use various different substances as replacements for water, such as glycerol or DMSO, and there's a frog that loads its own blood with carbohydrates at low temperatures in order to turn it into a better cryonic medium.

footnote

*The disruption of a cell's organization at extreme cold is likely to persist even if the cell is brought back to room temperature. See Gulevsky, et al for a complete review of the thermodynamics of cold denaturation.

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