Phosphoryl group-transfer potential

In the second glycolytic reaction that generates a compound with high phosphoryl group transfer potential, enolase promotes reversible removal of a molecule of water from 2-phosphoglycerate to yield phosphoenolpyruvate (PEP) ... 

Reaction 7 is an example of a substrate-level phosphorylation. Because the synthesis of ATP is endergonic, it requires an energy source. In substrate-level phosphorylations, ATP is produced because of the transfer of a phosphoryl group from a substrate with a high phosphoryl group transfer potential. Because two molecules of glycerate-l,3-bisphosphate are formed for every glucose molecule, this reaction... 

PEP has a higher phosphoryl group transfer potential than does glycerate-2-phos-phate because it contains an enol-phosphate group instead of a simple phosphate ester. The reason for this difference is made apparent in the next reaction. Aldehydes and ketones have two isomeric forms. The enol form contains a carbon-carbon double bond and a hydroxyl group. Enols exist in equilibrium with the more stable carbonyl-containing keto form. The interconversion of keto and enol forms, also called tautomers, is referred to as tautomerization ... 

Because ATP can transfer a phosphate group, we say that ATP has a high "phosphoryl group transfer potential" rather than calling it a high energy compound. The phosphate anhydride bonds of ATP, ADP,... 

Describe the structural and electronic bases for the high phosphoryl group-transfer potential of ATP, and give the free energy liberated by the hydrolysis of ATP under standard and cellular conditions. 

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