Final answer:
In the glycolytic pathway, a labeled 18O on the hydroxyl group of C3 in glucose will not appear in the resulting pyruvate but will be found in the water molecule formed as a byproduct.
Explanation:
If glucose is labeled with 18O on the hydroxyl group of C3, at the end of glycolysis the label will appear in the water molecule that is released when phosphoenolpyruvate is converted to pyruvate. During glycolysis, glucose undergoes a series of transformations, ultimately resulting in the production of pyruvate molecules. In the specific reaction where the label is transferred, the C3 hydroxyl oxygen is the one that ends up in the inorganic phosphate, which later reacts to form water.
The labeled oxygen atom from 18O is then incorporated into one of the phosphate groups of fructose-1,6-bisphosphate. As glycolysis continues, this labeled oxygen is eventually transferred to pyruvate, the end product of glycolysis.
Therefore, when considering the entire glycolytic pathway, the 18O label from C3 of glucose will not be found in the resulting pyruvate molecules, but rather in the byproduct water molecule.