If we are considering the instant before and after the death.
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There is no "instant". While you can describe a time of death, it is the point where the ability of the body to sustain function has failed to one of several possible endpoints, usually heartbeat. At the cellular level, the critical aspect is that the cellular energetics have broken down. The cell can no longer build itself up faster than it is breaking down. Even at this level, there is no instant. The cell may be able to retain some function even after it has reached the point of no return.
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As far as the atoms and molecules in cells are concerned, there's really no difference at all. Many of your cells stay alive for quite a while after you have died.