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Atomic Structure and Isotopes (4E) Practice Test
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Q1
In a metabolic tracing study, a researcher combusts purified glucose isolated from cells fed a mixture of $^{12}\text{CO}_2$ and $^{13}\text{CO}_2$. The CO$_2$ produced from combustion is analyzed by mass spectrometry, yielding two dominant peaks at 44.0 amu (assigned to $^{12}\text{C}^{16}\text{O}_2$) and 45.0 amu (assigned to $^{13}\text{C}^{16}\text{O}_2$). If the 45.0 amu peak has 25% of the intensity of the 44.0 amu peak, which statement about the carbon isotopes in the original glucose is most consistent with these results? (Use: $m(^{12}\text{C})=12.000$ amu, $m(^{13}\text{C})=13.003$ amu, $m(^{16}\text{O})=15.995$ amu.)
In a metabolic tracing study, a researcher combusts purified glucose isolated from cells fed a mixture of $^{12}\text{CO}_2$ and $^{13}\text{CO}_2$. The CO$_2$ produced from combustion is analyzed by mass spectrometry, yielding two dominant peaks at 44.0 amu (assigned to $^{12}\text{C}^{16}\text{O}_2$) and 45.0 amu (assigned to $^{13}\text{C}^{16}\text{O}_2$). If the 45.0 amu peak has 25% of the intensity of the 44.0 amu peak, which statement about the carbon isotopes in the original glucose is most consistent with these results? (Use: $m(^{12}\text{C})=12.000$ amu, $m(^{13}\text{C})=13.003$ amu, $m(^{16}\text{O})=15.995$ amu.)