We explore the reactivity of inorganic monophosphate ions (Pi) and 5′-adenosine monophosphate (AMP), adsorbed onto amorphous silica separately or together. This question has relevance for prebiotic chemistry scenarios and, more generally, for biomedical applications involving biomolecule adsorption. XRD, TGA, and 31P and 29Si NMR results show that inorganic phosphate ions deposited on silica condense to polyphosphates at considerably lower temperatures than in bulk KH2PO4. In the same temperature range, AMP adsorbed alone undergoes dismutation reactions, yielding adenosine, ADP, and ATP; in this case, the effect of the silica surface is not obvious. When AMP and Pi are coadsorbed on silica at high loadings (5-10%), AMP dismutation and phosphorylation by Pi both occur, allowing the formation of ADP and ATP. The latter result clearly shows the ability of silica surfaces to promote the formation of molecules generally considered as "high-energy" compounds and opens the way to further research on the effect of mineral surfaces for nucleotide synthesis and ribose stabilization.