Hey guys,

 

I am curious about the step of glucose-6-phosphate (herein g6p) to fructose-6-phospahate (herein f6p). I know that from glucose to g6p, it requires a molecule of ATP, along with hexokinase. And I also know that phosphoglucoisomerase is the enzyme from g6p to f6p, but does this require an input of energy?

 

And if it doesn't, can I assume that all the other steps through the glycolytic pathway that do not explicitly state the use of an energy intermediate is going to not require energy?

 

Michael

The step from glucose-6-p to fructose-6-p does not require ATP, it is an isomerase reaction (note that there is no addition of phosphate).

Then I can assume that Gly-4, Gly-5, and Gly-8 also do not require energy?

You may be misunderstanding the purpose of ATP in this context. It is probably confusing to think of ATP use as powering a process in this context. Rather it is easier to see as a transfer of a phosphate group to or from a metabolite. You can see that directly in the molecule.

Hey guys,

 

I am curious about the step of glucose-6-phosphate (herein g6p) to fructose-6-phospahate (herein f6p). I know that from glucose to g6p, it requires a molecule of ATP, along with hexokinase. And I also know that phosphoglucoisomerase is the enzyme from g6p to f6p, but does this require an input of energy?

 

And if it doesn't, can I assume that all the other steps through the glycolytic pathway that do not explicitly state the use of an energy intermediate is going to not require energy?

 

Michael

 

 

Glucose --> glucose 6 phosphate = transfer of γ-phosphate of ATP to glucose, using the energy from hydrolysis of γ-phosphate of ATP

 

Glucose 6 phosphate --> fructose 6 phosphate = isomerase reaction = net energy change is 0 kJ.mol^-1

 

Fructose 6 phsophate --> fructose 1, 6 bisphosphate = same principal as first reaction (transfer of a γ-phosphate from ATP, using the energy of hydrolysis of the γ-phosphate)

have anyone tried to check, it may be that those reactions that do not require ATP are either spontaneous or they may be powered by other means such as electrons or inorganic or organic element(s), and or compound(s); am not so sure but I think co-factors and co-enzymes may be responsible.

Evans7, There is at least one error in your thinking, and perhaps more than one. Enzymes and cofactors (coenzymes or metal ions) are catalysts that don't change the equilibrium constants of the reactions with which they are associated. Of the reactions in glycolysis that do not consume or produce ATP, some have favorable and some have unfavorable values of deltaG°'.

Edited March 31, 201510 yr by BabcockHall