Thermodynamic parameters (entropy, enthalpy, free energy, and internal energy) are given for an unknown enzyme. Explain which results would be expected for the breaking of hydrogen bonds and the exposure of hydrophobic groups from the interior during the unfolding process of a protein.
A) Entropy change, ΔS, is zero
B) Enthalpy change, ΔH, is positive
C) The reaction is spontaneous
D) Enthalpy change, ΔH, is negative
E) Entropy change, ΔS, is positive

Question

Quizplus · Accepted Answer

Unfolding of a protein involves breaking of hydrogen bonds and exposure of hydrophobic groups from the interior, which leads to an increase in entropy (disorder) of the system. Therefore, the entropy change, ΔS, is expected to be positive. The enthalpy change, ΔH, could be either positive or negative depending on the specific enzyme and the conditions of the experiment. However, since the reaction is spontaneous (i.e. favorable), the free energy change, ΔG, must be negative, which means that ΔH-TΔS is negative. Thus, if ΔS is positive, then ΔH must be negative to ensure a negative ΔG.

Thermodynamic Parameters (Entropy, Enthalpy, Free Energy, and Internal Energy) Are