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One of the reactions of glycolysis (a pathway of metabolism) involves the isomer

ID: 958761 • Letter: O

Question

One of the reactions of glycolysis (a pathway of metabolism) involves the isomerization of dihydroxyacetone phosphate (DHAP) to glyceraldehyde 3-phosphate (GAP). This reaction is a reversible (DHAP <----> GAP). When the reaction reaches equilibrium, the concentrations are: [DHAP] = 2 x 10-4 M, and [GAP] = 9.5 x 10-6 M. What are the values [write the numbers and units] for the following thermodynamic parameters? Show all work.

A) Equilibrium constant: Keq = ________

B) Reaction free energy at equilibrium: G = _________

C) Reaction free energy at standard state (T = 298K, [DHAP] = [GAP] = 1 M): Go = _________

Explanation / Answer

DHAP <-----------------> GAP

A)

[DHAP] = 2 x 10^-4 M

[GAP] = 9.5 x 10^-6 M

Keq = [GAP] / [DHAP]

= 9.5 x 10^-6 / 2 x 10^-4

= 0.0475

Keq = 0.0475

B)

Go = - RT ln Keq

= - 8.314 x 10^-3 x 298 x ln 0.0475

= 7.55 kJ/mol

Go = 7.55 kJ / mol

C)

if  [DHAP] = [GAP] = 1 M then Keq =1

Go = 0