Question

If O2 is supplied to yeast cells where the oxygen atoms are a heavy isotope (18O), where will the heavy oxygen atoms end up as a result of cellular respiration (using glucose as a fuel source)? Explain. (Hint: Begin by writing out the equation for cellular respiration).

Answer 1

The equation of cellular respiration

C6H12O6 + 6O2 ------------ 6CO2+ 6H2O + 36ATP

So the heavy isotope of oxygen -18 is highlighted as red and normal glucose oxygen as black.

The oxygen provided in this case is isotopic. So the isotopic oxygen ends up as H2O during cellular respiration. As the glucose uses its oxygen to make it CO2 , so it was also need isotopic 6 oxygen atoms from O2 as well . So it ends up as both carbon-dioxide and water.

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