In a key reaction of glycolysis, dihydroxyacetone phosphate (DHAP) is isomerized

Question

In a key reaction of glycolysis, dihydroxyacetone phosphate (DHAP) is isomerized into glyceraldehyde 3-phosphate (G3P) by the action of the enzyme triose phosphate isomerase:
  

DHAP <--------> G3P G = +7.5 kj/mol

Because G°’ is positive, the equilibrium lies to the left. (a) Calculate the equilibrium constant for this reaction, assuming a temperature of 37 °C. (b) In the cell, depletion of G3P makes the reaction proceed. What is the value of G if the concentration of G3P is kept at 1/100 of the value of the concentration of DHAP?

Explanation / Answer

a) delta G0 = -R*T*lnKeq ; where R = Universal Gas constant = 8.314 J/mole/K ; T = temperature in kelvin

or, lnKeq = -delta G0/(RT)

or, Keq = e-{delta G0/(r*t)} ; Put R = 8.314 & T = 310 K and the value of delta G0 in J to get the answer

b) delta G = delta G0 - R*Tln{[G3P]/[DHAP]}

or, delta G = delta G0 - R*Tln(1/100)

or, delta G = delta G0 + 11869.09 ; put the value of delta G0 in Jto get the result.

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