Difference Between Exergonic and Endergonic Reactions

Two kinds of reactions are described by the words endergonic and exergonic. Many chemical and biological interactions occur continually both within and outside the human body. Some of them are impulsive, while others are not. And, in the world of thermal and physical chemistry, these reactions are almost universal and occur often in one form or another.

This article uses a descriptive table to distinguish the fundamental and advanced distinctions between the two reactions for ease of learning and comprehension by a novice as well as a chemical enthusiast.

Exergonic Reactions vs Endergonic Reactions

The main difference between exergonic reactions and endergonic reactions is that exergonic reactions are spontaneous i.e. occur without insertion of energy or catalyst naturally whereas the endergonic reactions are nonspontaneous in nature hence, an external source of energy is provided to start the functioning of these types of chemical reactions.

Exergonic vs Endergonic Reactions

A reaction that generates free energy is known as an ‘exergonic’ reaction. Since this reaction produces energy rather than consuming it, it may happen on its own, without the intervention of other forces.

Exergonic reactions in biochemistry, as well as thermochemistry, are those in which the change in free energy is negative (minus in numerical value). The total quantity of energy accessible in a system is measured by free energy; negative changes indicate that energy has been discharged, while positive changes indicate that energy has been conserved.

An endergonic reaction necessitates the absorption of energy. These are not involuntary reactions that are nonspontaneous. To get started, they need exertion or a force input – mainly in the form of energy. Often the energy required to start the reaction is all that is needed, whereas other times the reaction absorbs energy during the whole process.

The common role of an endergonic reaction is to liberate energy from carbohydrate molecules or any supposed food molecule, allowing creatures to thrive without relying solely on sunlight for energy.

Comparison Table Between Exergonic and Endergonic Reactions

Parameters of ComparisonExergonic ReactionsEndergonic Reactions
DefinitionExergonic reactions are the spontaneous reactions that give out energy in the form of heat or vapour.Endergonic reactions are also known as nonspontaneous reactions or unfavourable reactions. The reaction necessitates further energy than you receive
Gibbs Free EnergyValue of Gibbs Free Energy is negative.Value of Gibbs Free Energy is positive.
Entropy LevelThe level of entropy is increased in a typical exergonic reaction.Entropy is decreased in an endergonic reaction.
Energy RequirementGives out energy usually in the form of heat.Intakes energy through the surroundings for initiation of the reaction or the continuation of it.
ExamplesThe reaction of sodium and chlorine to make table salt, combustion, and chemiluminescence. In this reaction energy is released in the form of light.The chemical reaction of photosynthesis is a good example for endergonic reactions.

What is Exergonic Reactions?

Exergonic are irreversible reactions that occur naturally in the environment. The term “spontaneous” refers to something ready or eager to occur with little or no external stimulation.

When subjected to oxygen in the atmosphere, sodium, for example, will burn. Another instance of exergonic reactions is the smoking of wood. In the study of chemical thermodynamics, such processes are referred to as favorable reactions since they produce more heat.

Under standard temperature and pressure, the Gibbs free energy is zero, indicating that more heat is taken than absorbed. These are responses that cannot be reversed. Exergonic reactions are those in which covalent bonds are disrupted, unleashing the energy stored in those interactions. Catabolism — the destructive portion of metabolism – refers to these chemical breakdown processes.

Living organisms employ exergonic processes to transport energy from “storage” in one component, such as fat or sugar, to an activated state, such as ATP. This would be accomplished by dissolving the sugar or fat covalent bonds and transferring its energy to a molecule called in the kind of electrons or another currency.

Gibbs’s free energy is negative. Because spontaneous reactions have a minus Gibb’s energy numeric value, when computed using the thermodynamics relationship, this implies that an exergonic reaction is always a spontaneous reaction or crafted or induced reaction.

What is Endergonic Reactions?

A process in which heat or any form of energy is absorbed is known as an endergonic reaction. This means that the overall change in free energy is positive in chemical terms.

Many processes in nature can only take place if adequate energy from the environment is available. These processes can’t happen on their own since they take a lot of energy to dissolve the chemical bonds.

External energy aids in the dissolution of these connections. The energy released as a result of the bond breaking then fuels the reaction. The energy produced during the breakdown of chemical bonds is sometimes insufficient to keep the reaction going. External energy is necessary for such circumstances to keep the reaction continuing.

A spontaneous reaction is indicated by a minus (-) Gibbs free energy. In the instance of endergonic reactions, this Gibbs free energy is positive (+), indicating that the reaction is not spontaneous. Unfavorable responses are another word for non-spontaneous reactions.

For the advancement of a non-spontaneous reaction, energy needs are given externally. As a result, the energy per unit is greater than the amount of the reactants. As a result, the change in enthalpy is a positive number.

Main Differences Between Exergonic and Endergonic Reactions

  1. Exergonic reactions give out energy whereas endergonic reactions require energy externally for the reaction to occur.
  2. Exergonic reactions are spontaneous whereas endergonic reactions are nonspontaneous.
  3. Exergonic reactions have a positive Gibbs Free Energy value whereas the endergonic reactions have a negative Gibbs Free Energy value.
  4. In exergonic reactions entropy increases whereas in endergonic reactions entropy decreases.
  5. The energy of the products of an exergonic reaction is more than the reactants whereas the energy of products is less than the reactants in the case of endergonic reactions.


Many reactions take place in nature and even inside our bodies to dissipate energy or to break down some covalent bonds for an essential process and these reactions vastly consist of either spontaneous or nonspontaneous nature.

Both exergonic and endergonic reactions mostly occur when the reaction is in equilibrium, hence they are very much occurring inside your body while you’re reading this article! Both the reactions involve changes in the Gibbs Free Energy and the difference in their entropies makes them polar opposite to each other. When considering thermodynamic chemistry, both the reactions can be further classified under endothermic and exothermic reactions based on intake and expelling of energy only in the form of heat energy.


  1. https://www.khanacademy.org/science/biology/energy-and-enzymes/free-energy-tutorial/a/gibbs-free-energy
  2. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/6%3A_Metabolism/6.2%3A_Potential_Kinetic_Free_and_Activation_Energy/6.2A%3A__Free_Energy
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