Calculate the actual, physiological ΔG for the reaction: creatine phosphate + ADP → creatine + ATP at 37°C, as it occurs in the cytosol of neurons with creatine phosphate at 4.7 mM, creatine at 1.0 mM, ADP at 0.73 mM, and ATP at 2.6mM. Give your answer in kJ/mol to one decimal point.

-13.2 kJ/mol

Explanation:

Creatine Phosphate  +  H₂O ------>   Creatine + P₁ (ΔG° = -43 kJ/mol

ADP                             +  Pi    ------->   ATP +  H₂O   ΔG° =  +30.5 kJ/mol    

Creatine Phosphate  + ADP  ------> Creatine  + ATP     ΔG° = -12.5 kJ/mol

Parameters given include:

Creatine Phosphate = 4.7 mM

creatine = 1.0 mM

ADP = 0.73 mM

ATP = 2.6mM

Temperature (T) = 37°C = (37+273)K = 310 K

ΔG° = -12.5 kJ/mol = -12500 J/mol

Rate constant (R) = 8.314

The actual physiological ΔG for the reaction can be determined using the formula:

ΔG = ΔG° + RT㏑

Replacing our values from above, we have:

ΔG =  - 12500  + (8.314)(310)㏑

ΔG =  - 12500 + 2577.34 × ㏑ [ 0.7578]

ΔG =  - 12500 + 2577.34 ( -0.2773)

ΔG = - 13214.696 J/mol

ΔG = - 13.215 kJ/mol

ΔG = - 13.2 kJ/mol    

∴  the actual, physiological ΔG for the reaction = - 13.2 kJ/mol ( to 1 decimal place)

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