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.

Pathway

Heme degradation & bilirubin (jaundice) · Macrophages of spleen, liver (Kupffer) and marrow → plasma (albumin) → hepatocyte smooth ER → bile → colon → stool and urine. Enzymes sit beside the arrows; a ★ marks the rate-limiting step. The map scrolls inside its panel.

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Heme degradation & bilirubin (jaundice)

Biliverdin (green)

Made from Senescent RBC heme (~120 days) by Heme oxygenase (microsomal) ★

Heme oxygenase (microsomal) ★ rate-limiting · irreversible — Heme degradation & bilirubin (jaundice)

Cofactors: O₂, NADPH

Heme → biliverdin + CO + Fe²⁺. The CO is the basis of the exhaled-CO test for hemolysis; iron is recycled. ~80–85% of bilirubin comes from old RBCs, the rest from ineffective erythropoiesis, myoglobin and cytochromes.

Condition cards:Pre-hepatic (hemolytic) jaundice →Hereditary spherocytosis (as cause of hemolytic jaundice) →Autoimmune hemolytic anemia (as cause of hemolytic jaundice) →Hemolytic disease of the newborn (ABO/Rh incompatibility) →

Becomes Unconjugated bilirubin (yellow, lipophilic) via Biliverdin reductase

Biliverdin reductase — Heme degradation & bilirubin (jaundice)

Cofactors: NADPH

Green → yellow — the colour change of a healing bruise.