Frequently Asked Question

The 14C label will be detected in pyruvate at the carboxyl group (C-1) after galactose passes through glycolysis. Here's why:
1. Galactose Entry: Galactose enters glycolysis after being converted to glucose-6-phosphate. The C-4 carbon in galactose becomes the C-6 carbon in glucose-6-phosphate.
2. Glucose-6-phosphate Isomerization: Glucose-6-phosphate is converted to fructose-6-phosphate. The C-6 carbon remains unchanged in this step.
3. Fructose-1,6-bisphosphate Formation: Fructose-6-phosphate is phosphorylated at C-1, generating fructose-1,6-bisphosphate. The C-6 carbon remains unaffected.
4. Glyceraldehyde-3-phosphate and Dihydroxyacetone Phosphate: Fructose-1,6-bisphosphate is cleaved into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The C-6 carbon of fructose-1,6-bisphosphate is now the C-3 carbon of glyceraldehyde-3-phosphate.
5. Glyceraldehyde-3-phosphate Oxidation: Glyceraldehyde-3-phosphate is oxidized to 1,3-bisphosphoglycerate. The C-3 carbon is oxidized to a carboxyl group, which becomes the C-1 carbon of 1,3-bisphosphoglycerate.
6. Pyruvate Formation: Through a series of steps, 1,3-bisphosphoglycerate is converted to pyruvate. The C-1 carbon, initially labeled with 14C, remains as the carboxyl group of pyruvate.