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Questions and Answers
The equation for Gibbs Free Energy is ΔG = ΔH − TΔS, where ΔG represents the change in ______.
Gibbs Free Energy
For ATP conversion to ADP + Pi, the standard Gibbs Free Energy change (ΔG°) is ______ kJ mol−1.
-30.5
The enthalpy change (ΔH°) for the same reaction is ______ kJ mol−1.
-20.1
At 37 °C, the calculated entropy change (ΔS°) for the reaction is ______ J mol−1.
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For the unfolding of a protein, ΔH° is ______ kJ mol−1.
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The entropy change (ΔS°) for protein unfolding is ______ J K−1 mol −1.
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To find the temperature at which the unfolding of a protein is spontaneous, we need to solve for ______ in the Gibbs Free Energy equation.
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For the unfolding to be spontaneous, ΔG must be ______.
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Study Notes
Gibbs Free Energy
- Gibbs free energy (G) is a thermodynamic potential that can be used to predict the spontaneity of a process
- The change in Gibbs free energy (ΔG) is negative for spontaneous processes (favorable) and positive for non-spontaneous processes (unfavorable).
- ΔG = ΔH - TΔS where:
- ΔH: Change in enthalpy
- ΔS: Change in entropy
- T: Temperature in Kelvin
ATP Hydrolysis
- ATP hydrolysis (ATP → ADP + Pi) releases free energy, with a standard free energy change (ΔG°) of -30.5 kJ mol-1 at 37°C.
- The enthalpy change (ΔH°) of -20.1 kJ mol-1 indicates the process is exothermic (releases heat)
- The entropy change (ΔS°) is positive (+34.0 J mol-1) suggesting increased disorder when ATP is hydrolyzed into ADP and inorganic phosphate.
- The combination of negative enthalpy change and positive entropy change contributes to the highly negative free energy change, indicating the process is highly favorable.
Protein Unfolding
- Protein unfolding is the process where a protein loses its three-dimensional structure and becomes disordered.
- The enthalpy change (ΔH°) for protein unfolding is positive (250.8 kJ mol-1) indicating the process requires heat input (endothermic).
- The entropy change (ΔS°) for protein unfolding is also positive (752 J K-1 mol-1) indicating an increase in disorder as the protein unfolds.
- Protein unfolding becomes spontaneous above a certain temperature, because the positive entropy term becomes more dominant at high temperatures.
- This is because ΔG is negative for the unfolding process when TΔS > ΔH.
- The temperature at which protein unfolding becomes spontaneous is:
- Calculated by setting ΔG to 0 and rearranging the equation: T = ΔH/ ΔS
- This yields a temperature of approximately 333 K (60°C).
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Description
Test your understanding of Gibbs Free Energy, including its role in predicting spontaneity of processes. This quiz covers key concepts such as ATP hydrolysis and protein unfolding, with a focus on thermodynamic principles like enthalpy and entropy changes.
