Question

Which of the listed hydrolysable compounds cannot be used as a coupling partner for the chemical synthesis of ATP (ADP + Pi + H+→ ATP + H2O)?

Question 2 options:

Glucose-1-phosphate (DGo' = -21.0 kJ/mol )


Acetyl-CoA (DGo' = -31.4 kJ/mol )


Phosphoenolpyruvate (DGo' = -61.9 kJ/mol)


1,3 bis-phosphoglycerate (DGo' = -49.3 kJ/mol )


Phosphocreatine (DGo' = -43.0 kJ/mol )

Answer 1

Glucose-1-phosphate cannot be used as a coupling partner for ATP synthesis because its free energy release upon hydrolysis is less than the energy required to synthesize ATP.

Step-by-step explanation:

The hydrolysable compound that cannot be used as a coupling partner for the synthesis of ATP (ADP + Pi + H+ → ATP + H2O) must have a lower free energy of hydrolysis than that of the formation of ATP. Given that the hydrolysis of ATP releases about -30.5 kJ/mol under standard conditions, and the synthesis of ATP from ADP and Pi is an endergonic process requiring an input of free energy, we need to use a compound with a greater free energy release upon hydrolysis compared to that required for ATP synthesis to drive the reaction forward.

Glucose-1-phosphate, with a ΔGo' of -21.0 kJ/mol, does not provide enough energy to synthesize ATP, as its free energy release upon hydrolysis is less than the -30.5 kJ/mol needed. Therefore, it cannot be used as a coupling partner for ATP synthesis in biological systems, unlike the other listed compounds, which all have higher free energy changes and can potentially drive the formation of ATP.