Final answer:
Two molecules of phosphoglyceraldehyde are produced in glycolysis during the cleavage of fructose-1,6-bisphosphate, marking the end of its energy-consuming phase.
Step-by-step explanation:
The two phosphoglyceraldehyde molecules in glycolysis are produced during the cleavage of fructose-1,6-bisphosphate. This process begins when glucose-6-phosphate is converted into fructose-6-phosphate, which is then phosphorylated again to form fructose-1,6-bisphosphate. The enzyme aldolase then cleaves this molecule into one molecule of glyceraldehyde-3-phosphate and one molecule of dihydroxyacetone phosphate. Through an isomerization reaction, the latter is converted into a second molecule of glyceraldehyde-3-phosphate. This step marks the end of the energy-consuming phase of glycolysis and sets the stage for the energy-yielding phase.