Consider the formation of a dimeric protein: 2 P ⟶P2 At 25^∘...

Consider the formation of a dimeric protein: $$ 2 \mathrm{P} \longrightarrow \mathrm{P}_{2} $$ At $25^{\circ} \mathrm{C},$ we have $\Delta H^{\circ}=17 \mathrm{kJ} / \mathrm{mol}$ and $\Delta S^{\circ}=65 \mathrm{J} / \mathrm{K} \cdot$ mol. Is the dimerization favored at this temperature? Comment on the effect of lowering the temperature. Does your result explain why some enzymes lose their activities under cold conditions?

Consider the formation of a dimeric protein:
$$
2 \mathrm{P} \longrightarrow \mathrm{P}_{2}
$$
At $25^{\circ} \mathrm{C},$ we have $\Delta H^{\circ}=17 \mathrm{kJ} / \mathrm{mol}$ and $\Delta S^{\circ}=65 \mathrm{J} / \mathrm{K} \cdot$ mol. Is the dimerization favored at this temperature? Comment on the effect of lowering the temperature. Does your result explain why some enzymes lose their activities under cold conditions?

Key Concepts

Enzyme Structure-Function Relationship

Many enzymes require a specific quaternary structure, such as dimerization, to achieve their active conformation and function correctly. Changes in temperature can influence this oligomeric state by altering the balance between enthalpy and entropy contributions. At lower temperatures, the decreased T?S may make the formation of active dimeric structures less favorable, potentially leading to a loss in enzymatic activity.

Protein Dimerization and Oligomerization

Protein dimerization is the process by which two protein molecules associate to form a single dimer, a type of oligomerization. The thermodynamic stability of this assembly is dictated by the balance between enthalpic and entropic changes during the association. Even if the process is endothermic (positive ?H), a sufficiently large positive ?S, when amplified by a high enough temperature, can drive the formation of the dimer.

Gibbs Free Energy

Gibbs free energy (?G) is the key thermodynamic quantity that determines whether a reaction is spontaneous. It is calculated with the equation ?G = ?H - T?S, where ?H is the change in enthalpy and ?S is the change in entropy. For a reaction to be favored under a given set of conditions, ?G must be negative, signifying that the energy released by the process outweighs the energy required.

Temperature Dependence in Thermodynamics

Temperature is a crucial factor in assessing reaction spontaneity because it scales the impact of the entropy change (T?S) on the overall free energy. In reactions where both ?H and ?S are positive, as temperature increases, the T?S term can outweigh the endothermic ?H, making the reaction spontaneous. Conversely, lowering the temperature diminishes the contribution of entropy, potentially making an otherwise favorable reaction non-spontaneous.

Transcript

Please give Ace some feedback