Re: My question is in the comments, it doesn't fit here.

Endergonic means that the process requires an input of energy to proceed.  
Let me interpret your question as what I think you are asking.

Unfavorable, energy-requiring reactions can be driven forward by coupling 
them to a favorable one.  In biochemistry, many such reactions are driven 
by breaking the reactive, unstable bonds of ATP, which has two 
phosphoanhydride bonds and one phosphate ester bond.  Sometimes people call 
such bonds energy-containing, but that is technically incorrect.  Many 
enzymes can transfer one of these bonds to their substrate (the reactant, 
the thing that is acted on by the enzyme), often through a very short-lived 
bond with the enzyme itself, which then transfers the bond to the 
substrate.  The substrate then is in a position to go forward to the 
product, again with the help of the enzyme.  The final result is what is 
called hydrolysis of ATP, since ultimately by the end of the whole reaction 
sequence the unstable bonds are transferred to water (hydrolysis = "cutting 
by water").  Often, the reaction is meant to connect two substrates 
together, with ATP being used up as just described.

So:  in endergonic reactions that put two substrates together, you need two 
binding sites for the substrates that will go to the product, and one 
binding site for ATP.  You often need reactive groups on the enzyme itself 
to attack the ATP.  All of this means that you have more than one site 
where action is taking place.