= Substrate-level phosphorylation
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<Substrate-level phosphorylation> forms <ATP> by <enzyme>-catalyzed transfer of a <phosphate> group from a phosphorylated <substrate> to <ADP>. In canonical <glycolysis>, two such transfers occur for each three-<carbon> route, giving four gross <ATP> per <glucose>. Unlike <oxidative phosphorylation>, these transfers do not require an <electron transport chain>.<Biology 2e by Mary Ann Clark and others>[§7.2, steps 7 and 10: phosphate transfer to ADP; §7.5, opening comparison of fermentation with respiration]{ref}
The <pyruvate kinase> example under <Coupled-enzyme readout of glycolytic ATP formation> separates the material transfer from its detection. A favourable coupled <chemical reaction> supplies the driving change in <Gibbs free energy>; the <enzyme> supplies a catalytic route. Counting <ATP>-forming transfers gives a gross yield, while subtracting upstream <ATP> use gives the net yield.
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