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Would deuterated water, being heavier, slow down the metabolic rate of the cell and subsequently the aging process?

edit: lets say I wanted to observe a cellular event, like the formation of the blsatopore or ameboid motion, could I soak a cell in a solution with D2O without killing it or severely damaging it ?

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Yes it would, by a few percent. It may or may not be a goal worth pursuing, but there is more to it.

Different reactions would be slowed down to a different extent. Tiny as they are, these discrepancies suffice to disrupt the delicate biochemical machinery of the living cell. No life form more advanced than bacteria is OK with that. Deuterated water in high concentrations is unpleasant for plants and downright lethal for animals, including us.

So much for your slowed aging.

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  • $\begingroup$ wait, why would it be lethal for animals? its not like it admits radioactive decay? $\endgroup$ – Confusedbyeverything Jul 23 '17 at 8:37
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    $\begingroup$ @Confusedbyeverything, different reactions are slowed down by different amounts. Bacteria can handle this; humans can't. $\endgroup$ – Mark Jul 23 '17 at 10:37
  • $\begingroup$ To add a bit of nuance, you need quite a bit of deuterated water to notice this. In the short term, drinking 5 liters of D2O is about as harmful as drinking 5 liters of H2O. You need to consume D2O over a longer period to replace a significant fraction of the H2O in your body before the specific effects become noticeable. $\endgroup$ – MSalters Jul 23 '17 at 22:55
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    $\begingroup$ Out of curiosity, could you add some references for the effect on deuterated water on plants and animals? In particular, what is the typical cause of death? $\endgroup$ – tomasz Jul 23 '17 at 23:34
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Yes, the kinetic isotope effect is the main reason due to the differential lowering of the zero point energy in reactants and transition state, which has the effect of increasing, slightly, the activation energy. However, this effect is small, a few percent in a single reaction. The reason that deuteration has an effect overall is due to the fact that biochemical pathways involve many intermediate steps each of which has a small isotope effect. The total effect is multiplicative.

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