Question

If the ΔG°' for ATP hydrolysis is –30 kJ/mol and the ΔG°' for phosphoenolpyruvate hydrolysis is –62 kJ/mol, what is the ΔG°' for the phosphorylation of ADP by phosphoenolpyruvate?

a) -32 kJ/mol

b) -62 kJ/mol

c) +31 kJ/mol

d) +92 kJ/mol

e) -92 kJ/mol

Please provide the appropriate calculation and show the reactions that are involved + the overall reaction. Thank you!

Answer 1

1. The given reactions are: ATP+H,O=ADP+P Phosphoenolpyruvate +,0 =pyruvate+ P AGº'= -30kJ/mol ... (1) AGⓇ-62kJ/mol.... (2) To calculate the AGº' value for the following reaction: Phosphoenolpyruvate +ADP pyruvate+ATP AGº'=-62kJ/mol b) Gibbs energy is an extensive property so, when the number of moles of reactants and products changes, the value of AG also changes. For the reverse reaction the sign of the AG is changed. Reverse equation (2) as shown below: ADP+P = ATP+H2O AGⓇ'= -30kJ/mol Phosphoenolpyruvate + H2O =pyruvate + AGⓇ'=-62 kJ/mol Phosphoenolpyruvate + ADP = pyruvate + ATP AGº'=-32 kJ/mol Therefore, AGⓇ value for the reaction is -32kJ/mol. The correct answer is A.