1.6.2 Hydrolysis & Synthesis of ATP

Hydrolysis of ATP:

• ATP (adenosine triphosphate) is broken down into ADP (adenosine diphosphate) and an inorganic phosphate (Pi)****.
• This reaction is catalysed by the enzyme ATP hydrolase.
• Energy is released during this process because:
  • The bonds between the phosphate groups are unstable, with low activation energy, allowing them to be broken easily.
  • When these bonds break, a large amount of energy is released.

Uses of Released Energy:

• The released inorganic phosphate can be used to phosphorylate other molecules.
  • This makes the molecules more reactive, aiding in processes such as:
  • Enzyme activity.
  • Cellular reactions (e.g., glycolysis in respiration).

Synthesis of ATP:

• ATP is reformed from ADP and inorganic phosphate in a condensation reaction.
• This reaction is catalysed by the enzyme ATP synthase.
• Synthesis occurs during:
  • Respiration (oxidative phosphorylation in mitochondria and substrate-level phosphorylation in glycolysis).
  • Photosynthesis (photophosphorylation in chloroplasts).