Question

The free-energy change for the formation of a protein from the individual amino acids is positive and is thus an endergonic reaction. how, then, do cells accomplish this process?

Answer 1

Answer;

-The endergonic (thermodynamically unfavorable) reaction is coupled to an exergonic, (thermodynamically favorable) reaction through a shared intermediate, so that the overall free-energy change of the coupled reactions is negative (the overall reaction is exergonic).

Explanation;

-Protein folding is a highly complex process by which proteins are folded into their biochemically functional three-dimensional forms. The hydrophobic force is an important driving force behind protein folding.

-Protein folding is entropically unfavorable because it minimizes the dispersal of energy and adds order to the system. However, the summation of the hydrophobic effect, hydrogen bonding, and van der Waals forces is greater in magnitude than the loss of entropy. Protein folding is therefore a spontaneous process because the sign of ΔG (Gibbs free energy) is negative.

Answer 2

An endergonic reaction, like photosynthesis, refers to a reaction, which needs the energy to be driven. The activation energy for the reaction is usually greater in comparison to the entire energy of the exergonic reaction. The endergonic reactions are non-spontaneous.

In the given case, in order to accomplish the process, the coupling of the endergonic reaction, that is, thermodynamically unstable reaction with an exergonic, that is, the thermodynamically stable reaction is done so that the entire free-energy change of the coupled reactions becomes negative.