TBL3 Question 4

[Xiaolu Xu]

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TBL 2 Team 4:

“The [products]_ss/[reactants]_ss of an in vivo reaction is 0.001. The equilibrium constant for the reaction is 1000. Is the in vivo reaction reversible or irreversible? Explain your answer by calculating  ∆G in vivo and comparing it to K_eq ?

 

DG=DG°+2.3RTlog ([Product]_ss/[Reactant]_ss)                        Eqn. 1

DG°= -2.3RTlog ([Product]_eq/[Reactant]_eq)                        Eqn. 2 (@equilibrium DG=0)

 

Step 1:

Using Eqn 2 and given [Product]_eq/[Reactant]_eq =10^3

DG°= -1.36log (10^3) à DG°= - 4.08

 

Step 2:

Using Eqn 1 and given [Product]_ss/[Reactant]_ss =10^ -3 and using DG°= - 4.08 (from the previous step

DG= - 4.08 + 1.36log (10^ -3)

DG= - 4.08 + -4.08 à DG°= - 8.16

 

According to the slide from lecture…

 

The reaction is Irreversible because K_ss    or [Product]_ss/[Reactant]_ss  < K_eq or [Product]_eq /[Reactant]_eq , meaning that it is far from equilibrium.