How is ATP Hydrolysed?

ATP (adenosine triphosphate) is hydrolysed through metabolic processes to release energy for cellular work. Here's a detailed breakdown:

Understanding ATP Hydrolysis

ATP hydrolysis involves breaking down the ATP molecule by adding water. This process is not a single step; it often involves the sequential removal of phosphate groups.

The Process

• ATP to ADP: Initially, ATP is hydrolysed to ADP (adenosine diphosphate) by breaking the bond between the terminal phosphate group and the rest of the molecule. This reaction releases a free inorganic phosphate (Pi) group and a considerable amount of energy.

  • Reaction: ATP + H₂O → ADP + Pi + Energy

• ADP to AMP: ADP can be further hydrolyzed to AMP (adenosine monophosphate) also releasing a phosphate group and energy.

  • Reaction: ADP + H₂O → AMP + Pi + Energy

Energy Release

• The process of ATP hydrolysis to ADP is energetically favorable, yielding a Gibbs-free energy of -7.3 cal/mol. [1] This negative value indicates that the reaction is exergonic, meaning it releases energy that cells can use to perform various functions.

  • The energy released from ATP hydrolysis powers many cellular activities, including:
    • Muscle contraction.
    • Active transport of molecules across cell membranes.
    • Synthesis of biomolecules.

Why ATP is Constantly Replenished

Cells cannot store large amounts of ATP because it is unstable and needs to be continuously replenished. The constant cycle of ATP hydrolysis and replenishment ensures that the cell has the necessary energy supply.

Summary Table

Reaction	Products	Energy Released
ATP → ADP + Pi	ADP + Phosphate	Yes (-7.3 cal/mol)
ADP → AMP + Pi	AMP + Phosphate	Yes

Key Concepts

• Metabolic Processes: ATP hydrolysis is a central part of cellular metabolism, providing the energy needed for various biological functions.
• Gibbs-Free Energy: The change in Gibbs-free energy during ATP hydrolysis indicates the energy that is available to do work.