Question

Standard Free Energy of Hydrolysis, ∆ G ^o', of some organophosphate compounds (phosphate isreleased as one of the products of hydrolysis)                                    

Compound	kJ/mol
phosphoenolpyruvate	-61.9
carbamyl phosphate	-51.4
creatine phosphate	-43.1
acetyl phosphate	-42.2
ATP (to ADP)	-30.5
Glucose-1-phosphate	-20.9
Glucose-6-phosphate	-13.8
Glycerol-3-phosphate	-9.2

Use the table in the above table to calculate the ∆G ^o' (in kJ/mol) for the following reaction:

ATP +  glucose --------> ADP  +  glucose-6-phosphate

Answer 1

Given reaction , occurs in two steps.

1) ATP + H₂O -> ADP + phosphate

For this reaction of hydrolysis of ATP ,from table

ΔGo₁ = -30.5 KJ/ mol.

2) Glucose + phosphate -> Glucose - 6 - Phosphate + H₂O

This reaction is reverse to hydrolysis of glucos - 6 - phosphate.

So , for this reaction ΔGo₂ = - ( - 13.8) = +13.8 KJ/mol

So for overall reaction of

ATP+ Glucose -> ADP + Glucose -6- phosphate

ΔGo =  ΔGo₁ + ΔGo₂

= -30.5 +13.8

= - 16.7 KJ/ mol.