Gibbs free energy question with relation to ATP hydrolysis. Relevant information

Question

Gibbs free energy question with relation to ATP hydrolysis.

Relevant information:

The standard free energy for ATP hydrolysis: ATP + H2O ? ADP + H2PO4 is -30.5 kJ/mol assume this occurs at 298.15 kelvin

2.b. Typical intracellular concentrations of ATP, ADP and H2PO4 in muscle are 5.0 mM, 0.5 mM and 1.0 mM, respectively. What is the free energy of hydrolysis (AG) at these concentrations? 2.c. What would the concentrations of ATP and ADP be, if the hydrolysis reaction were to reach equilibrium at 25 C? (Ignore any contribution of AMP and assume that inorganic phosphate is constant at 1.0 mM).

Explanation / Answer

2b]

ATP + H2O ADP + H2PO4

K = [H2PO4-] * [ADP] / [ATP] = 0.5*1*10^-6 / 5*10^-3 = 0.0001

delta G = delta Go + RT lnK

delta G = -30.5KJ + 298*8.314*ln 0.0001 = -53.319 KJ

2c]

detla Go = -RT lnKeq

-30.5KJ = -8.314*298*ln Keq

Keq = 222001 =  [H2PO4-] * [ADP] / [ATP]

[ADP] / [ATP] = 2.22*10^9

The ratio can only be found

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