Question

The value of ΔG°\' for the conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate (GAP) is 7.53 kJ/mol. If the concentration of dihydroxyacetone phosphate at equilibrium is 2.65 mM, what is the concentration of glyceraldehyde-3-phosphate?

Assume a temperature of 25.0 °C. The constant R = 8.3145 J/(mol·K)

[GAP] = ??? mM

Answer 1

The overall reaction of the conversion of DHAP to glyceraldehyde- 3- phosphate is as follows Triose phosphate nisomerase Glyceraldehyde 3-phosphate phosphate The relationship between the standard free energy change and the equilibrium constant is given by the following equation AG AG +RTln K. At equilibrium, AG 0 then AG-RTln K, 9 The equilibrium constant (Ka^) for the reaction where DHAP is converted to form glyceraldehyde- 3- phosphate in presence of enzyme called triose phosphate isomerase at 25°C can be calculated by using the following formula Where , Ris the gas constant 8.315 J. K1mol , Tis the temperature 25°C 298K AG7.53 kJ. mol7530 J.mol1 Substitute the values in the above equation (7530 J mo) (8.315 J.K-1. molt x298 K) e17530/24779) -3.04 -0.048

Hence, the value of the equilibrium constant for the given reaction at 25°C is l0.048 [Glyceraldehyde-3-phosphate] DHAP eg Equate equilibrium constant value with the above equation. According to the given information, the concentration of DHAP is 2.65 mM. 0.048 x 0.048x2.65x10-3 M 2.65 x10 M 0.0001272 M -0.127 mM Thus, the concentration of glyceraldehyde- 3-phosphate is 0.127 mM