Why can't dead cells come back to life?

If something critical is missing from the cell, the processes needed to keep the cell in proper working order - maintaining concentrations of ions, intake of energy, maintaining pressures - are disrupted and something in the cell breaks, and that's what kills the cell. If a lack of oxygen killed the cell, it's not like the cell went on pause, something was destroyed. Adding oxygen back to the cell doesn't fix what was degenerated.

Sometimes they do come back to life. think of people who were legally dead, but due to medical intervention they are brought back to life. It just depends on your definition of dead. If youre dead too long, the tissues in the brain etc. die from lack of oxygen. After a certain point, too much of you has suffered irreversible damage. Some frogs have evolved a type of antifreeze, and during winter months they are basically dead, they hibernate and the antifreeze (ethylene glycol) in their bodies preserves them and keeps the cells from developing ice crystals and exploding. That is one example of many where the line between life and death isnt clearly defined. Great question!

Cells either die because they are damaged causing them to no longer be able to perform their function or because of apoptosis, which is basically self-destruction. http://www.scientificamerican.com/article.cfm?id=why-does-programmed-cell READ.

Really good question. Let's start simple. I think the best definition of life is a self-sustaining series of chemical reactions. Chemical reactions are occurring and, provided with proper nutrition (oxygen, amino acids, glucose, parts to make membranes, etc.) can survive for anywhere from a few minutes to a century. The big problem with this idea of yours is that protein pumps, which require energy, play a major part in the cell (and the generation of energy). If you deprive the cell of vital nutrients (oxygen, as in your example) such that it can't make energy then it will use all of its energy up. When you reintroduce oxygen, there is no ATP left to run these protein pumps, so these nutrients can't get back in to the cell. Furthermore, the reactions which generate energy require energy input (less than the output). But, deprived for a long enough period of time, there is no ATP left to start the chemical reactions to generate more energy. Excellent question, something that I had never thought about before.

more cells come from the dead cells

Let me give you a more "detail" explanation than the rest of these people. You need oxygen to for oxidation/phosphorylation, i.e to make ATP. if you stop producing atp, you don't have the essential energy source to run those chemical reactions. When those reactions stop, enzymes get denature and their 3d shape changes and are not longer able to bind with their substrate. If you don't have enzymes working in the cell, you don't have chemical reactions occurring. hence you you die

In the process of cellular respiration, Oxygen is needed to provide energy for the cell to function. When they Oxygen is absent, cells can respire anaerobically which means without oxygen but eventually the cell dies and the energy is stopped being produced. When oxygen become present again, the cell is already dead so there is no effect on the cell. Hope this helps.

well there is alot of cells in you body some are your skin and some are your organs but still all the cells will die because there is new cells that can take its place.ex you skin is just a tissue that falls off all the time and you dont even know the dust in you house is the dead skin cells that has fallen off so ya there also your blood cell your body make so many blood cells that will go though your heart and everything else they make so much blood because when you have a bad fall you might bleed and you need some blood to renew wat you have lost and some go with the waste that you body thoughs away

they sorta can...ever heard of cryonics?