= Glucose 1-phosphate
\b[Glucose 1-phosphate] is a <glucose>-derived <phosphate ester> with phosphate attached through the oxygen at carbon1, the <anomeric carbon> in the cyclic sugar. The attachment position is part of its identity: <glucose-6-phosphate> has the phosphate at a different carbon. An explicit example is α-D-glucose 1-phosphate, whose ChEBI record specifies the α configuration at the anomeric center.<Alpha-D-glucose 1-phosphate in ChEBI>[CHEBI:29042, Definition, structure and IUPAC Name]{ref}
The neutral acid representation in that record has <molecular formula> $\mathrm{C_6H_{13}O_9P}$. This counts one phosphorus atom per sugar unit; proton loss changes charge and hydrogen count without moving the phosphate attachment. Distinguishing the <anomer>, attachment position and protonation state is more informative than reporting only total phosphorus.<Alpha-D-glucose 1-phosphate in ChEBI>[Formula, Net Charge and conjugate-base relation]{ref}
A biological example is production of α-D-glucose 1-phosphate by <glycogen phosphorylase>. The enzyme transfers a terminal glucosyl unit from a suitable <glycogen> chain to inorganic <phosphate>; this is <phosphorolysis>, rather than simple release of free <glucose> by <hydrolysis>.<Enzyme Nomenclature by the IUBMB>[EC 2.4.1.1, Reaction and Comments; https://iubmb.qmul.ac.uk/enzyme/EC2/4/1/1.html]{ref}
For an original assay-accounting example, a reaction extent of $2\,\mu\mathrm{mol}$ for this one-unit cleavage consumes $2\,\mu\mathrm{mol}$ inorganic <phosphate> and forms $2\,\mu\mathrm{mol}$ <glucose 1-phosphate>. It transfers phosphorus between free and sugar-bound pools without changing the total phosphorus in a closed sample. A total-phosphorus assay could therefore remain constant while a molecule-specific assay detects product formation. The stated extent is a bookkeeping example, not a predicted yield near <glycogen> branch points or at <chemical equilibrium>.
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