ATP hydrolysis is accompanied by the release of a proton to the aqueous medium (water solvent!). ATP-4 + H2O → ADP-3 + HPO4-2 + H+ b) Why might the level of hydrolysis change at these 2 specific pH values? Let's include the value of protons in the free energy equation, and we'll use -30.5 kJ/mol as the standard state value. a) Determine the ΔG of ATP hydrolysis at pH 7 and then again at pH 2. d) Knowing the relationship between ATP and Phosphocreatine, what mass of creatine phosphate must be used to make the daily requirement of ATP (if this was the only source of ATP! It's not)
Added by Richard L.
Step 1
First, we need to find the ΔG of ATP hydrolysis at pH 7 and pH 2. We know that the standard state value is -30.5 kJ/mol. We also know that ΔG = ΔG° + RT ln(Q), where R is the gas constant (8.314 J/mol K), T is the temperature in Kelvin (assume 298 K), and Q is the Show more…
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The standard free energy of hydrolysis (ΔG°') of ATP is -32.2 kJ/mol. ATP + H2O → ADP + Pi. The actual free energy of ATP hydrolysis, represented by ΔG, depends on the intracellular concentrations of reactants and products. Calculate ΔG for ATP hydrolysis at 37 °C using the following concentrations of ATP, ADP, and Pi: [ATP] = 2.25 mM; [ADP] = 0.25 mM; [Pi] = 1.65 mM.
Sri K.
The free energy change for ATP hydrolysis is -30.5 kJ/mol under standard conditions, but the actual free energy of hydrolysis (ΔG'°) of ATP in living cells is very different because the cellular concentrations of ATP, ADP, and Pi are not identical and are much lower than the 1.0 M of standard conditions. The actual free energy of hydrolysis of ATP under intracellular conditions is often called its phosphorylation potential, ΔGp. Calculate the actual free energy of hydrolysis of ATP, ΔGp, in human erythrocytes at pH 7.0 and the temperature 37°C (body temp). The concentrations of ATP, ADP, and Pi in human erythrocytes are 2.25, 0.25, and 1.65 mM, respectively. Hint: ΔGp = ΔG'° + RT ln [ADP][Pi]/[ATP] What does this reveal about the amount of energy required to synthesize ATP under the physiological conditions?
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