Biology – Respiration | e-Consult

The splitting of fructose 1,6-bisphosphate (F1,6BP) into two triose phosphate (G3P) molecules is catalyzed by the enzyme aldolase. This is a β-elimination reaction.

Mechanism: Aldolase facilitates the cleavage of the carbon-carbon bond between carbons 2 and 3 of F1,6BP. This results in the formation of two molecules of G3P. The reaction proceeds through an unstable intermediate where a proton is transferred, and the bond is broken. The reaction is reversible, but under the conditions of glycolysis, it is essentially irreversible.

Crucial for Efficiency: This step is crucial because it converts a 6-carbon molecule into two 3-carbon molecules. This is essential for the subsequent oxidation reactions in the energy-payoff phase. By producing two G3P molecules per F1,6BP molecule, glycolysis can generate two molecules of ATP and two molecules of NADH per glucose molecule. Without this step, the process would be far less efficient in extracting energy from glucose.