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In chemical thermodynamics, an endergonic reaction (from Greek ἔνδον (endon) 'within' and ἔργον (ergon) 'work'; also called a heat absorbing nonspontaneous reaction or an unfavorable reaction) is a chemical reaction in which the standard change in free energy is positive, and an additional driving force is needed to perform this ...
The reaction will only be allowed if the total entropy change of the universe is zero or positive. This is reflected in a negative ΔG, and the reaction is called an exergonic process. If two chemical reactions are coupled, then an otherwise endergonic reaction (one with positive ΔG) can be made to happen.
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]
[1] [2] These reactions require energy, known also as an endergonic process. [3] Anabolism is the building-up aspect of metabolism , whereas catabolism is the breaking-down aspect. Anabolism is usually synonymous with biosynthesis .
An electron transport chain (ETC [1]) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H + ions) across a membrane.
One manifestation of this is enzymes or receptors that have multiple binding sites where the affinity of the binding sites for a ligand is apparently increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to a binding site. For example, when an oxygen atom binds to one of hemoglobin's four binding ...
The isolated reaction of anabolism is unfavorable in a cell due to a positive Gibbs free energy (+ΔG). Thus, an input of chemical energy through a coupling with an exergonic reaction is necessary. [ 1 ] : 25–27 The coupled reaction of the catabolic pathway affects the thermodynamics of the reaction by lowering the overall activation energy ...
For exergonic and endergonic reactions, see the separate articles: Endergonic reaction; Exergonic reaction; See also. Exergonic process; Endergonic; Exothermic process;