ATP can be used to drive reactions that would otherwise be e

ATP can be used to drive reactions that would otherwise be energetically unfavorable. How does ATP do this? A. It is converted into cAMP and then phosphorylates an enzyme. B. It transfers its terminal phosphate to one of the substrates. C. It transfers all of its phosphates to an enzyme. D. It covalently attaches to substrates, generating products. E. It covalently attaches to an enzyme, speeding up its action.

Solution

Answer: (B) It transfers its terminal phosphate to one of the substrates.

Phosphoryl froup transfer is a common means of energy coupling. ATP in particularly is an efficient phosphoryl-group donor and transfers its terminal phosphate to one of the substrates to drive an unfavourable reaction.

Three factors are important:

Resonance stabilization, electrostatic repulsion, and stabilization due to hydration. ADP and, particularly, Pi, have greater resonance stabilization than does ATP. Orthophosphate has a number of resonance forms of similar energy, whereas the -phosphoryl group of ATP has a smaller number. This explains the structural basis of the high phosphoryl transfer potential of ATP