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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.

Pathway

Heme synthesis (porphyrias) · Mitochondria (steps 1, 6–8) and cytosol (steps 2–5); ~85% in marrow erythroid precursors, the rest mostly liver (P450 turnover). Enzymes sit beside the arrows; a ★ marks the rate-limiting step. The map scrolls inside its panel.

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Heme synthesis (porphyrias)

Heme

Made from Protoporphyrin IX by Ferrochelatase

Ferrochelatase · irreversible — Heme synthesis (porphyrias)

Cofactors: Fe²⁺

Inhibited by: LEAD — lead-sensitive step #2

Deficiency: Erythropoietic protoporphyria (marrow origin) — painful, burning photosensitivity WITHOUT frank blistering from childhood; protoporphyrin in RBCs and skin; hepatobiliary disease from biliary protoporphyrin in severe cases

Inner mitochondrial membrane. When iron can't be inserted, zinc is — zinc protoporphyrin is the lab marker.

Condition cards:Erythropoietic protoporphyria (EPP) →