A direct measurement of the standard free energy

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Unformatted text preview: for ATP Hydrolysis. A direct measurement of the standard free-energy change associated with the hydrolysis of ATP is technically demanding because the minute amount of ATP remaining at equilibrium is difficult to measure accurately. The value of G’º can be calculated indirectly, however, from the equilibrium constants of two other enzimatic reactions having less favorable equilibrium constants: Glucose 6-phosphate+ H2O ——> Glucose 1-phosphate ;Keq= 270 ATP + glucose ———————-> ADP + glucose 6-phosphate; Keq= 890 Using this information for equilibrium constants determined at 25 ºC, calculate the standard free energy of hydrolysis of ATP. G'1 = (-2.48 kJ/mol)(ln270) = -14 kJ/mol G'2 = (-2.48 kJ/mol)(ln890) = -17 kJ/mol G'sum = G'1 + G'2 = -31 kJ/mol 4. (15%) The G’º for Coupled Reactions. Glucose 1-phosphate is converted in to fructose 6-phosphate in two successive reactions: a) Glucose 1-phosphate ——–> glucose 6-phosphate G1 = -7.3 kJ/mol b) Glucose 6-phosphate ——-> fructose 6-phosphate G2 = 1.7 kJ/mol 1 Calculate the equilibrium constant, K...
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