a) Label the following reactions as spontaneous or nonspontaneous: creatine phos

Question

a) Label the following reactions as spontaneous or nonspontaneous:

creatine phosphate + H2O creatine + Pi                                                                                        

ADP + Pi ADP + H2O                                                                                                                  

b) Calculate the G° and Keq for the following reactions (i and ii). Are they spontaneous or nonspontaneous?

i) creatine phosphate + ADP creatine + ATP

G°:                                                   

Keq :                                                   

Spontaneous: Yes/No

ii) creatine + ATP creatine phosphate + ADP

G°:                                                   

Keq :                                                   

Spontaneous: Yes/No

Explanation / Answer

A reaction is spontaneous depending upon the sign of standard gibbs free energy change. If it is -ve, the reaction is spontaneous or else it is not spontaneous.

creatine phosphate + H2O creatine + Pi, deltaG( standard gibbs free energy change ) = -10.3 kcal/mol (1). Hence spontaneous.

ADP+PI---->ATP+H2O deltaG = 7.3 Kj/mole (2). Hence non spontaneous.

Addition of Eq.1 and Eq.2 gives Creatine Phosphate+ADP ----->Cretaine+ATP deltaG= -10.3+7.3= -3 Kj/mole. Spontaneous. since deltaG =-RTlnK

lnK= -deltaG/RT = 3*1000/(8.314*298) , K= Equilibrium constant = 3.356

Reversing it gives Creatine+ATP----->Creatine phosphate+ADP, deltaG= 3 Kj/mole Nonspontaneous

lnK = -detaG/RT = -3*1000/(8.314*298) =0.29794

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