The direct phosphorylation of glucose by inorganic phosphate is
a thermodynamically unfavorable reaction:
glucose+Pi→glucoseglucose+Pi→glucose-66-phosphate+H2Ophosphate+H2O
ΔG∘′=+3.3kcal/molΔG∘′=+3.3kcal/mol
In the cell, glucose phosphorylation is accomplished by coupling
the reaction to the hydrolysis of ATPATP, a highly exergonic
reaction:
ATP+H2O→ADP+PiATP+H2O→ADP+Pi
ΔG∘′=−7.3kcal/molΔG∘′=−7.3kcal/mol
Typical concentrations of these intermediates in yeast cells are as
follows:
[glucose-6-phospate] = 0.08mMmM
[ATP]=1.8mM[ATP]=1.8mM
[Pi]=1.0mM[Pi]=1.0mM
[ADP]=0.15mM[ADP]=0.15mM
Assume a temperature of 25∘C∘C for all calculations.
What minimum concentration of glucose would have to be maintained in a yeast cell for the coupled reaction to be thermodynamically spontaneous?
Minimum concentration of Glucose is 7.712 nM
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