Learn / Metabolism
Metabolic pathways
Every FMK pathway as a clickable map. Pick one pathway to hammer it — next step, enzyme, regulator, cofactor, and the facts that get tested (NADPH and who needs it, rate-limiting steps, deficiencies) — or set it to all pathways for a mixed drill. Every answer says which enzyme and which pathway.
Pyrimidine synthesis (& thymidylate) · Cytosol, essentially all cells (CAD, UMP synthase); dihydroorotate dehydrogenase on the inner mitochondrial membrane. Enzymes sit beside the arrows; a ★ marks the rate-limiting step. The map scrolls inside its panel.
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Pyrimidine synthesis (& thymidylate)
UMP
Made from OMP by OMP decarboxylase (UMP synthase, activity 2)
OMP decarboxylase (UMP synthase, activity 2) — Pyrimidine synthesis (& thymidylate)
Either UMP synthase activity lost → orotic aciduria. Orotic aciduria WITH hyperammonemia is OTC deficiency instead (mitochondrial carbamoyl phosphate overflows into this pathway).
Condition cards:Ornithine transcarbamylase (OTC) deficiency →
Becomes UDP via UMP kinase
UMP kinase — Pyrimidine synthesis (& thymidylate)
Cofactors: ATP