Coupled and Coupling Reactions

Is Coupling Reactions, Heck Reaction for example, different from Coupled Reactions like the production of Glucose 6-phosphate in living organism?




A simplistic answer is as follows (though, please do refer to [the](http://en.wikipedia.org/wiki/Coupling_reaction) [links](http://en.wikipedia.org/wiki/Endergonic_reaction) given by Greg in a comment to the question):


According to the University of Wisconsin page [Coupling Reactions](http://www.chem.wisc.edu/deptfiles/genchem/netorial/modules/thermodynamics/altdefs/coupling.htm), **coupling reactions** are



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> a reactant-favored reaction is linked to a product-favored reaction so that both reactions yield products.
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A main point in the related [University of Wisconsin website](http://www.chem.wisc.edu/deptfiles/genchem/netorial/modules/thermodynamics/free/free05.htm) is that if the reaction is reactant-favoured ($\Delta{G} > 0$), then it is not going to happen, so it is coupled with a product-favoured reaction ($\Delta{G} < 0$), leading to **coupled reactions** are



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> When chemical reactions are coupled, the free energy released by the exergonic reaction is used to drive the endergonic one toward the formation of products.
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where the overall reation is product-favoured.


(The website uses an analogy of a coupled train).


A great explanation is in [this YouTube clip](http://www.youtube.com/watch?v=-ZndltxrNqY) from Dr. John Pollard, of the University of Arizona.


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To cite the [Oxford Dictionary of Biochemistry and Molecular Biology (2006 - 2nd edition)](https://www.oxfordreference.com/view/10.1093/acref/9780198529170.001.0001/acref-9780198529170) :


"**coupled reaction** either of two reactions, one endergonic and the other exergonic, that are linked energetically, occur simultaneously, and *share a common intermediate*, such that the overall free energy change for the two reactions is negative." (the *highlight* is by me)


"**coupling** **1** (in chemistry) the covalent linking of one chemical entity to another; see **covalent bond**."


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