= Adenosine diphosphate
{title2=$\mathrm{ADP}$}
{wiki}
= ADP
{c}
{synonym}
<ADP> contains the same <adenosine> unit as <ATP>, with two <phosphate> groups instead of three. One <ATP> converted by the stated <hydrolysis> gives one <ADP> and one <inorganic phosphate>: $3=2+1$ accounts for the <phosphate> groups while <adenine> and <ribose> are retained. <ADP> is therefore a reusable material carrier, rather than <ATP> with its entire structure discarded.
Regeneration reverses the net <chemical reaction>:
$$
\mathrm{ADP}+\mathrm P_i\longrightarrow\mathrm{ATP}+\mathrm{H_2O}.
$$
At the same stipulated reference conditions its $\Delta G^{\circ\prime}$ is $+30.5\,\mathrm{kJ\,mol^{-1}}$, the negative of the <hydrolysis> value. It is an <endergonic reaction> and requires <energy> input through <energy coupling>; a <catalyst> alone cannot supply that input. Recycling the material carrier does not recycle the expended driving <energy>. <Cellular respiration> and <light-dependent reactions> supply routes for regeneration. See https://www.ncbi.nlm.nih.gov/books/NBK9903/[Cooper, The Cell: ATP generation and energy coupling].
<ADP> is a <nucleotide> with two <phosphate> groups. Formation of <ATP> from <ADP> and <phosphate> couples to <energy> supply in <light-dependent reactions>; the <Calvin cycle> returns <ADP> after using <ATP>. https://openstax.org/books/biology-2e/pages/8-3-using-light-energy-to-make-organic-molecules[OpenStax Biology 2e, 8.3: recycling ATP and ADP]{ref}.
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