Question: The ΔG°’ for the conversion of fructose 1,6-bisphosphate (FBP) into glyceraldehyde-3- phosphate (…

The ΔG°’ for the conversion of fructose 1,6-bisphosphate (FBP)
into glyceraldehyde-3- phosphate (GAP) and dihydroxyacetone
phosphate (DHAP) is +5.7 kcal/mol. This reaction is step four of
the glycolytic pathway and is catalyzed by aldolase. In the cell at
37 °C, the mass action [DHAP]/[GAP] = 5.5

a. What is the equilibrium concentration of [FBP] when [GAP] =
1.8 x 10-5 M, assuming that the mass action between DHAP and GAP is
maintained?

b. What is the actual concentration of [FBP] when [GAP] = 1.8 x
10-5 M, given that the observed ΔG’ = -0.3 kcal/mol, assuming that
the mass action between DHAP and GAP is maintained?

c. Since the standard state free energy for this step is
positive, does it need to be coupled to ATP hydrolysis to proceed
spontaneously? Explain why or why not.