2. The direct phosphorylation of glucose by Pi is a thermodynamically unfavorabl

Question

2. The direct phosphorylation of glucose by Pi is a thermodynamically unfavorable reaction. In the cell, glucose phosphorylation is accomplished by coupling the rxn to the hydrolysis of ATP. (See both reactions below) Rxn #1 glucose + P-> glucose-6-P + H2O G": +3.3 kcal/mol Rxn #2 ATP + H2O ? ADP + P AG 7.3 kcal/mol Typical concentrations of the intermediates in yeast cells at 25°C are [glucose-6-Pl 0.07 mM ATP]- 1.9 mM [ADP]-0.13 mM [PJ-1.1 mM a) Write the overall chemical equation for the coupled (ATP-driven) phosphorylation of glucose. What is the ?G for the coupled reaction? (2pts) b) What minimum concentration of Rlucose would have to be maintained in a yeast cell for the coupled reaction to be thermodynamically spontaneous? Is this physiologically reasonable? (hint..u.se your chemical egn for the coupled reaction and your calculated ?G" from part a to set up your calculation, what should you set &G;, to to solve the problem for Iglucose) and spontaneity?). (5pts)

Explanation / Answer

A) Chemical equation for the coupled reaction is -

Glucose+ATP = Glucose-6-P +ADP. And the gibbs free change energy for the coupled reaction is -4.0 kcal/mol .

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