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)

Bilirubin–albumin (plasma)

Made from Unconjugated bilirubin (yellow, lipophilic) by Binds albumin for transport

Binds albumin for transport — Heme degradation & bilirubin (jaundice)

Unconjugated ('indirect') bilirubin is lipophilic, water-insoluble, crosses the blood–brain barrier — neurotoxic — and is NOT filtered into urine (acholuric jaundice when it rises).

Condition cards:Kernicterus (bilirubin encephalopathy) →Drug displacement of bilirubin from albumin (salicylates, sulfonamides) →

Becomes Hepatocyte bilirubin (ligandin) via Sinusoidal uptake (OATP) → ligandin (Y protein)

Sinusoidal uptake (OATP) → ligandin (Y protein) — Heme degradation & bilirubin (jaundice)

Deficiency: Rotor syndrome (AR) — defective hepatic storage/OATP transport: benign conjugated hyperbilirubinemia, liver NOT pigmented (vs Dubin-Johnson)

Facilitated transport across the basolateral membrane; ligandin shuttles it to the smooth ER.

Condition cards:Rotor syndrome →