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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)

Coproporphyrinogen III

Made from Uroporphyrinogen III by Uroporphyrinogen decarboxylase (UROD)

Uroporphyrinogen decarboxylase (UROD) — Heme synthesis (porphyrias)

Deficiency: Porphyria cutanea tarda (the MOST common porphyria; often acquired with hepatitis C, alcohol, estrogen, iron overload) — blisters and skin fragility on sun-exposed skin, hypertrichosis, onset 4th–5th decade; tea-coloured urine with ↑ uroporphyrin that fluoresces coral-pink under Wood's lamp; no acute attacks; treat with phlebotomy, low-dose hydroxychloroquine, treat HCV

4 acetate → methyl. Cytosol.

Condition cards:Porphyria cutanea tarda (PCT) →

Becomes Protoporphyrinogen IX via Coproporphyrinogen oxidase

Coproporphyrinogen oxidase — Heme synthesis (porphyrias)

Cofactors: O₂

Deficiency: Hereditary coproporphyria (AD) — straddles the line: acute neurovisceral attacks AND cutaneous photosensitivity

Re-enters the mitochondrion; 2 propionate → vinyl.

Condition cards:Hereditary coproporphyria (HCP) →