Explain what is meant by the hydrolysis of ATP and describe how the products of this reaction are used to regenerate ATP.

AQA A-Level Biology (7402) — 3.1.6 ATP · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

Hydrolysis of ATP is the addition of a water molecule to the terminal phosphate bond, breaking the bond and splitting ATP into ADP and inorganic phosphate (Pi). The breaking of this high‑energy bond releases energy.

The released energy is used in cellular respiration to power the synthesis of ATP from ADP and Pi. In a condensation (phosphorylation) reaction, ADP and Pi are joined together, forming a new high‑energy phosphate bond and regenerating ATP.

Examiner tips

  • Use the term ‘hydrolysis’ and mention water and bond breaking. Include the products ADP and Pi. State that energy is released. Explain that this energy drives the condensation reaction. Mention respiration as the source of energy.

Common mistakes

  • Forgetting to mention water or bond breaking. Saying ATP is split into ATP and Pi. Not linking the energy release to the regeneration step.

Mark scheme (5 marks)

  1. Hydrolysis of ATP involves the addition of water / breaking of a bond / splitting of ATP
  2. ATP is broken down into ADP and inorganic phosphate (Pi)
  3. Energy is released when this bond is broken
  4. ADP and inorganic phosphate are recombined / condensation reaction joins them back together
  5. Energy from respiration is used to regenerate / re-synthesise ATP from ADP and Pi

Key terms in this question

hydrolysis · ATP

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