Explain why ATP is described as the 'energy currency' of the cell and describe what happens to ATP when it releases energy for use in cellular processes.

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)

ATP is the cell’s energy currency because it stores chemical energy that can be released for many processes. When a cell needs energy, ATP is hydrolysed to ADP and inorganic phosphate (Pi), releasing energy that is used for work such as muscle contraction, active transport and protein synthesis. The ADP and Pi can then be joined back together to reform ATP using energy from cellular respiration, allowing the cycle to repeat.

Examiner tips

  • Use the phrase ‘energy currency’ and explain it’s a universal source of energy
  • Show the hydrolysis reaction and the energy release
  • Mention ADP + Pi → ATP resynthesis via respiration
  • Link to examples of cellular processes

Common mistakes

  • Confusing ATP with ADP as the energy source
  • Omitting the hydrolysis reaction or the release of Pi
  • Not explaining that ATP can be resynthesised

Mark scheme (5 marks)

  1. ATP stores chemical energy (that can be released for cellular processes)
  2. ATP can be broken down to release energy / energy is released when ATP is hydrolysed
  3. ATP is broken down into ADP and inorganic phosphate (Pi)
  4. ATP can be resynthesised / ADP and Pi can be joined back together using energy (from respiration)
  5. ATP is described as energy currency because it is used / transferred throughout the cell as a universal source of energy for many different processes (e.g. muscle contraction, active transport, protein synthesis)

Key terms in this question

ATP

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