swollcat

5+ Year Member
Jan 18, 2014
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I was under the assumption that the hydrolysis of ATP, in other words the dissociation of ATP into ADP + P was a very favorable reaction with a negative delta G. The breaking of this bond is exergonic and releases energy.

According to a question I've run into, ATP has a positive BDE and the breaking of the bond requires energy as is the case with any catabolic reaction.

Can anyone please tell me why the bonds in between the phosphate groups have a positive BDE and require energy in order to dissociate? Who provides the energy to break the bond; hydrolysis?!
 
Jan 26, 2015
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MD/PhD Student
Quote from Wikipedia:

"The description and typical textbook labeling of ATP phosphanhydridic bonds as "high energy . . bonds" can be very misleading to students. These bonds are in fact relatively weak. They do involve high energy electrons but the bonds themselves are quite easy to break. As noted below, energy is released by the hydrolysis of ATP when these weak bonds are broken - requiring a small input of energy, followed by the formation of new bonds and the release of a larger amount of energy as the total energy of the system is lowered and becomes more stable."

You're right; hydrolysis of ATP is a favorable reaction with a negative delta G.
 

sazerac

rye sense of humor
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Feb 26, 2012
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Breaking any bond requires energy. Otherwise the bond would not exist in the first place.

In this specific instance, the ADP-Pi bond is broken via hydro-lysis (loosely translated from Greek as water-cutting). Water is broken into H and OH (which also requires energy input), and the the ADP and the Pi are combined with the OH and the H, and these two bond-forming reactions release a tremendous amount of usable energy.