The sum of the biosynthetic reactions leading from pyruvate to free blood glucose (Table 14-3) is
For each molecule of glucose formed from pyruvate, six high-energy phosphate groups are required, four from ATP and two from GTP. In addition, two molecules of NADH are required for the reduction of two molecules of 1,3-bisphosphoglycerate. Clearly, Equation 14-9 is not simply the reverse of the equation for conversion of glucose to pyruvate by glycolysis, which requires only two molecules of ATP:
The synthesis of glucose from pyruvate is a relatively expensive process. Much of this high energy cost is necessary to ensure the irreversibility of gluconeogenesis. Under intracellular conditions, the overall free-energy change of glycolysis is at least —63 kJ/mol. Under the same conditions the overall AG of gluconeogenesis is — 16 kJ/mol. Thus both glycolysis and gluconeogenesis are essentially irreversible processes in cells.
Was this article helpful?
I lost over 60 pounds and 4+ inches off my waist without pills, strenuous exercise, or any of the things that the diet experts tell you to do...and I did it in less than 4 months! If you have the desire, and can read through my e-book , then this is for you! I could have easily made it a lot more difficult, with stacks of information that people will never read, but why?