A "pulse-chase" experiment using 14C -labeled carbon sources is carried out on a yeast extract maintained under strictly anaerobic conditions to produce ethanol. In this experiment, a small amount of 14C -labeled glucose is incubated with the yeast just long enough for each intermediate molecule in the glycolysis pathway to become labeled. Assuming only one of glucose's carbons were labeled, where would the 14C have to be located in the starting glucose molecule (ie: what carbon number) in order to ensure that all the 14C carbon was liberated as14CO2 during fermentation to ethanol? Explain by indicating the labeled carbon through each of the intermediate structures.