Question

(2pts) I can purchase ATP powder from a supplier and resuspend the ATP in water at mM concentrations without safety concerns. This might be surprising given that ATF hydrolysis is highly exergonic under these conditions and releases considerable energy. How is this possible? Why doesn't the tube immediately combust upon addition of water? (2pts) Calculate AG at equilibrium for ATP hydrolysis - show your calculation for credit. Hint - think about this as if the cellular concentrations reached equilibrium.

Answer 1

Question 1 Answer- Your justification is right, hydrolysis of ATP is highly exergonic meaning that energy states of reactants are higher than the energy states of products, and hence the reaction is favorable and spontaneous. But for something to combust, it needs to cross an energy barrier known as Activation Energy, which can be overcome by the introduction of a catalyst that lowers the Activation Energy of combustion of ATP.

Question 2 Answer- Please not, Equilibrium means that the reaction is not favoring any particular direction (neither forward nor reverse), and in such a scenario deltaG should be equal to zero.

Also note, if delta G > 0, the reaction favors the forward direction i.e. reactants will tend to produce products.

           And if delta G < 0, the reaction favors the reverse direction i.e. products will tend to produce reactants.

      And if delta G= 0, the reaction will be at equilibrium i.e. it will not tend to go in either direction.