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)

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.