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An endergonic reaction (such as photosynthesis) is a reaction that requires energy to be driven. Endergonic means "absorbing energy in the form of work." The activation energy for the reaction is typically larger than the overall energy of the exergonic reaction (1). Endergonic reactions are nonspontaneous.
According to the IUPAC, an exothermic reaction is "a reaction for which the overall standard enthalpy change ΔH⚬ is negative". [4] Some examples of exothermic process are fuel combustion , condensation and nuclear fission , [ 5 ] which is used in nuclear power plants to release large amounts of energy.
The change of Gibbs free energy (ΔG) in an exergonic reaction (that takes place at constant pressure and temperature) is negative because energy is lost (2). In chemical thermodynamics, an exergonic reaction is a chemical reaction where the change in the free energy is negative (there is a net release of free energy). [1]
Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the hydrogen carrier NADPH and the energy-storage molecule ATP. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.
The entire reaction is usually catabolic. [13] The release of energy (called Gibbs free energy) is negative (i.e. −ΔG) because energy is released from the reactants to the products. An endergonic reaction is an anabolic chemical reaction that consumes energy. [3] It is the opposite of an exergonic reaction.
The nonequilibrium thermodynamic state in plants is achieved by continuous alternation of phases of solar energy consumption as a result of photosynthesis and subsequent biochemical reactions, as a result of which adenosine triphosphate (ATP) is synthesized in the daytime, and the subsequent release of energy during the splitting of ATP mainly ...
For exergonic and endergonic reactions, see the separate articles: Endergonic reaction; Exergonic reaction; See also. Exergonic process; Endergonic; Exothermic process;
The chain of redox reactions driving the flow of electrons through the electron transport chain, from electron donors such as NADH to electron acceptors such as oxygen and hydrogen (protons), is an exergonic process – it releases energy, whereas the synthesis of ATP is an endergonic process, which requires an input of energy.