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.
Heme degradation & bilirubin (jaundice)
Urobilinogen (colon, colourless)
Made from Bile → small intestine by Colonic bacteria (deconjugate & reduce)
Colonic bacteria (deconjugate & reduce) — Heme degradation & bilirubin (jaundice)
No bile reaching the gut (complete obstruction) → no urobilinogen → pale/clay-coloured (acholic) stool and absent urine urobilinogen.
Condition cards:Post-hepatic (obstructive) jaundice →Gallstone obstruction of the common bile duct (choledocholithiasis) →Pancreatic head cancer (malignant biliary obstruction) →Biliary atresia →Cholangiocarcinoma / primary sclerosing & biliary cholangitis →
Becomes Stercobilin → stool (brown) via Oxidation in the colon (~80–90%)
Oxidation in the colon (~80–90%) — Heme degradation & bilirubin (jaundice)
Gives stool its brown colour.
Becomes Urobilin → urine (yellow) via Reabsorbed (~10–20%) → mostly enterohepatic recirculation; a little reaches the kidney and is oxidised
Reabsorbed (~10–20%) → mostly enterohepatic recirculation; a little reaches the kidney and is oxidised — Heme degradation & bilirubin (jaundice)
Gives urine its yellow colour. ↑ in hemolysis (more substrate through a normal liver), absent in obstruction.