A student claims that ATP is not a store of energy but a transfer molecule. Justify whether this claim is correct.

AQA A-Level Biology (7402) — 3.1.6 ATP · Justify · 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 a transfer molecule, not a long‑term energy store.
1. It transfers energy from respiration to cellular processes.
2. It releases energy where it is needed in the cell.
3. It is synthesised during respiration from ADP + Pi.
4. It is hydrolysed to ADP + Pi, releasing energy for cellular processes.
5. ADP and Pi are rapidly recycled to re‑synthesise ATP, forming a continuous cycle.

Examiner tips

Use the word "transfer" to show understanding of the claim.
Show the cycle of synthesis and hydrolysis to cover all points.
Mention respiration as the source of energy.
Keep each point short and use correct terminology.

Common mistakes

Confusing ATP with glycogen as a long‑term store.
Omitting the synthesis step from ADP + Pi.
Using vague terms like "energy" without specifying hydrolysis.

Mark scheme (5 marks)

The claim is correct / ATP is a transfer molecule (not a long-term energy store)
ATP transfers energy from respiration to cellular processes / ATP releases energy where it is needed in the cell
ATP is synthesised during respiration (from ADP + Pi)
ATP is hydrolysed / broken down to ADP + Pi, releasing energy for cellular processes
ATP can be rapidly recycled / ADP and Pi are re-used to re-synthesise ATP, making it a continuous cycle

Key terms in this question

ATP