Question

The free-energy change, [delta] G, is positive for the cellular process of protein synthesis, so that this process is thermodynamically unfavorable even with the help of enzymes. How do cells still manage to synthesize proteins at such a high rate?

Answer 1

We know that if ,for a reaction,it will have a ,i.e the forward reaction is not favorable. The process of protein synthesis also have such a +ve but still the reaction is carried out by the cells in an efficient manner due to following reasons-

• The Endergonic reaction () is coupled with a suitable Exergonic reaction such that the energy required to make the reaction spontaneous in forward direction ,sometimes in many cases,ATP play a major role in coupling the two reactions,but in case of Protein synthesis,
• The two reactions(i.e. Endergonic and Exergonic) coupling takes place in the Ribosome ,active site of which is composed of RNA.RNA acts as an enzyme and fasten the process of peptide bond formation by-

1. suitable positioning of two substrates
2. lowering the activation energy of the reaction
3. positioning the water in the active site
4. stabilizing the intermediates by providing an electrostatic atmosphere.

Thus the unfavorable reaction (bond formation between amino acids) is coupled with a favorable hydrolysis of an aminoacyl-tRNA to make the overall .