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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 principle that biological macromolecules catalyze a thermodynamically unfavorable reaction if and only if a thermodynamically favorable reaction occurs simultaneously, underlies all known forms of life. The transfer of electrons from a donor molecule to an acceptor molecule can be spatially separated into a series of intermediate redox ...
A reaction with ∆H°<0 is called exothermic reaction while one with ∆H°>0 is endothermic. Figure 8: Reaction Coordinate Diagrams showing favorable or unfavorable and slow or fast reactions [7] The relative stability of reactant and product does not define the feasibility of any reaction all by itself.
Thermochemistry is useful in predicting reactant and product quantities throughout the course of a given reaction. In combination with entropy determinations, it is also used to predict whether a reaction is spontaneous or non-spontaneous, favorable or unfavorable. Endothermic reactions absorb heat, while exothermic reactions release heat ...
Anabolism usually involves reduction and decreases entropy, making it unfavorable without energy input. [6] The starting materials, called the precursor molecules, are joined using the chemical energy made available from hydrolyzing ATP, reducing the cofactors NAD + , NADP + , and FAD , or performing other favorable side reactions. [ 7 ]
Large particles are more energetically favorable since, continuing with this example, more atoms are bonded to 6 neighbors and fewer atoms are at the unfavorable surface. As the system tries to lower its overall energy, molecules on the surface of a small particle (energetically unfavorable, with only 3 or 4 or 5 bonded neighbors) will tend to ...
[4]: 5 Specifically, Van der Waals strain is considered a form of strain where the interacting atoms are at least four bonds away from each other. [5] The amount on steric strain in similar molecules is dependent on the size of the interacting groups; bulky tert-butyl groups take up much more space than methyl groups and often experience ...
Syntrophy, in the context of microbial metabolism, refers to the pairing of multiple species to achieve a chemical reaction that, on its own, would be energetically unfavorable. The best studied example of this process is the oxidation of fermentative end products (such as acetate, ethanol and butyrate ) by organisms such as Syntrophomonas .