Endergonic reactions (from the Greek. Ένδον - inside, internal and Greek. Έργον - work, action), as well as non-spontaneous reactions - according to the second law of thermodynamics, these are chemical reactions for which the flow of energy from the outside is necessary. The Gibbs free energy of such reactions is always positive, i.e. ΔG °> 0 . Endergonic reactions are associated with exergonic reactions, and cannot be carried out in principle without them. An example of such reactions can be the process of separating air into oxygen and nitrogen , where it is necessary to expend energy [1] , as well as anabolic processes occurring in living organisms: protein biosynthesis , gluconeogenesis , synthesis of fatty acids, ATP synthesis , and many others.
Thermodynamic description
Since ΔG °> 0, endergonic reactions cannot proceed spontaneously , they are thermodynamically disadvantageous. Therefore, for the implementation of such reactions requires an influx of energy. If the absolute value of ΔG ° is large, then such processes will not proceed at all [2] . The equilibrium constant of endergonic reactions is related to the value of the Gibbs free energy by the following equation:
where T is the absolute temperature , R is the universal gas constant equal to 8.3144 J / (mol * K). Given that the value of ΔG °> 0, then the equilibrium constant will be less than 1.
As a result, such reactions proceed from right to left (reverse reaction), that is, the equilibrium is greatly shifted towards the initial reagents.
See also
- Exergonic reactions
- Gibbs energy
- Chemical thermodynamics
Notes
- ↑ Godnev I.N., Krasnov K.S., Vorobyev N.K. Physical chemistry. - M .: Higher School, 1982. - p. 185. - 687 p.
- ↑ E.S. Severin. Biochemistry. - M: GEOTAR-MED, 2004. - 779 p. - ISBN 5-9231-0254-4 .