The first reaction in glycolysis is the phosphorylation of glucose to form gluco

Question

The first reaction in glycolysis is the phosphorylation of glucose to form glucose 6-phosphate: Pi  + glucose   glucose 6-phosphate + H2O This is a thermodynamically unfavorable reaction, with G°’ = +13.8 kJ/mol. a) In a liver cell at 37°C the concentrations of both phosphate and glucose are normally maintained at about 5 mM each. What is the equilibrium concentration of glucose 6-

phosphate, according to the above reaction?

b) This very low concentration of glucose 6-phosphate is unfavorable for glycolysis. In fact,

the reaction is coupled to the hydrolysis of ATP:

ATP + H2O   ADP + Pi  + H+ G°’ = -32.2 kJ/mol

Write the expression for the overall reaction and calculate G°’.

c) In addition to the glucose and phosphate concentrations listed in part (a) above, assume that the liver cell concentrations of ATP and ADP are 3 mM and 1 mM, respectively. Calculate the theoretical equilibrium concentration of glucose 6-phosphate at pH = 7.4

and 37 °C.

Explanation / Answer

The first reaction in glycolysis is the phosphorylation of glucose to form gluco

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