C1.2.1—ATP distributes energy

ATP distributes energy by moving small, soluble and reusable energy packets from respiration to cellular processes that require work, supporting usable cellular work and measurable biological activity.

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November 2025Paper1B ["SL"] · TZ33(e)[ 2 ]C1.2.1—ATP distributes energy

May 2011Paper1 ["SL"] · TZ112[ 1 ]C1.2.1—ATP distributes energy

Coverage 2011–2025 · Updated 15 Jul 2026

ATP is a small, soluble nucleotide found in all living cells. It transfers manageable amounts of energy between energy-yielding reactions and energy-requiring processes, and can move between nearby reaction sites in the aqueous cell.

$ATP + H_2O \rightarrow ADP + P_i$

$ADP + P_i \rightarrow ATP$

Cells recycle ATP rapidly rather than storing large reserves of it. Glucose, glycogen and lipids are more stable energy stores; respiration transfers some of their energy into ATP when and where work is needed.

organic substrate → stepwise oxidation in respiration → ATP regeneration → coupled transport, synthesis or movement → ADP + Pᵢ recycled

With adequate oxygen, aerobic respiration completes oxidation and yields much more ATP. Without enough oxygen, human cells can regenerate NAD through lactate formation so glycolysis continues, but only its small ATP yield remains.

Respiration rate can be estimated from O₂ uptake only when CO₂ is absorbed and temperature, pressure, organism amount and measurement time are controlled.

[ 3 ]

Explain the properties of ATP that make it useful for distributing energy within cells.

Concept essentials

ATP stores and distributes usable energy within cells.
ATP hydrolysis releases energy by conversion to ADP and phosphate.
ATP can be regenerated from ADP during respiration.
ATP powers processes such as ion pumping and resting potential maintenance.