Explain why cells need a continuous supply of ATP and describe two cellular processes that require 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).

Cells are constantly carrying out processes that require energy. This energy is supplied by ATP, which is produced during respiration.

Model answer (5 marks)

Cells cannot store large amounts of ATP – the store is limited and is rapidly depleted during use.
ATP is continuously hydrolysed to ADP and phosphate during cellular processes.
Therefore ATP must be continuously resynthesised from ADP and phosphate during respiration.
One process that requires ATP is muscle contraction.
A second process that requires ATP is active transport of ions across membranes.

Examiner tips

Use the exact terminology – ‘hydrolysed’, ‘resynthesised’, ‘ADP and phosphate’. Name two distinct processes – e.g. muscle contraction and active transport. Show the logical sequence: limited store → consumption → need for continuous synthesis.

Common mistakes

Saying ATP can be stored in large amounts. Using ‘energy’ instead of ‘ATP’ when describing processes. Naming the same process twice or giving a process that does not use ATP.

Mark scheme (5 marks)

ATP cannot be stored in large amounts / cells have a limited store of ATP
ATP is continuously broken down / used up during cellular processes
ATP must therefore be continuously remade / resynthesised from ADP and phosphate during respiration
One correct cellular process named that requires ATP, e.g. muscle contraction / active transport / protein synthesis / cell division
A second correct cellular process named that requires ATP, different from the first

Key terms in this question

ATP