[Campbell Biology P.201] In the ATP-coupled synthesis of glutamine Figure 8.10b , a phosphor... | Practice Question

In the ATP-coupled synthesis of glutamine Figure 8.10b , a phosphorylated intermediate Glu-P is formed. Why is the formation of this intermediate a crucial step for the reaction to proceed?

  • A: Glu-P is more stable and less reactive than glutamic acid, promoting product formation.
  • B: The phosphate group makes the intermediate more reactive by increasing its free energy, allowing ammonia to displace it.
  • C: The intermediate acts as a direct energy source, releasing ATP.
  • D: Its formation directly converts the endergonic reaction into an exergonic one without further steps.

Explanation

The formation of the phosphorylated intermediate Glu-P is crucial because the attached phosphate group makes the molecule less stable and more reactive with more free energy . This increased reactivity allows the subsequent displacement by ammonia to form glutamine to proceed more easily, effectively lowering the activation energy for the overall reaction in the coupled process.