Nucleotides are made from amino acids, carbon dioxide and formic acid in pathways that require large amounts of metabolic energy.[82] Consequently, most organisms have efficient systems to salvage preformed nucleotides.[82][83] Purines are synthesized as nucleosides (bases attached to ribose).[84] Both adenine and guanine are made from the precursor nucleoside inosine monophosphate, which is synthesized using atoms from the amino acids glycine, glutamine, and aspartic acid, as well as formate transferred from the coenzyme tetrahydrofolate. Pyrimidines, on the other hand, are synthesized from the base orotate, which is formed from glutamine and aspartate.[85]