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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.
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]
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.
Figure 6:Reaction Coordinate Diagrams showing reactions with 0, 1 and 2 intermediates: The double-headed arrow shows the first, second and third step in each reaction coordinate diagram. In all three of these reactions the first step is the slow step because the activation energy from the reactants to the transition state is the highest.
For exergonic and endergonic reactions, see the separate articles: Endergonic reaction; Exergonic reaction; See also. Exergonic process; Endergonic; Exothermic process;
Considering finite changes instead of infinitesimal changes, one can write the equation for the extent of a reaction as = The extent of a reaction is generally defined as zero at the beginning of the reaction. Thus the change of is the extent itself. Assuming that the system has come to equilibrium,
Tritium is a low-energy beta emitter commonly used as a radiotracer in research and in traser [check spelling] self-powered lightings.The half-life of tritium is 12.3 years. The electrons from beta emission from tritium are so low in energy (average decay energy 5.7 keV) that a Geiger counter cannot be used to detect the
Coupled with an endergonic reaction of anabolism, the cell can synthesize new macromolecules using the original precursors of the anabolic pathway. [11] An example of a coupled reaction is the phosphorylation of fructose-6-phosphate to form the intermediate fructose-1,6-bisphosphate by the enzyme phosphofructokinase accompanied by the ...