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.
Ethanol metabolism
Acetaldehyde
Made from Ethanol by Alcohol dehydrogenase (ADH)
Alcohol dehydrogenase (ADH) — Ethanol metabolism
Cofactors: NAD⁺ → NADH
Cytosol; zero-order kinetics at drinking concentrations. Fomepizole inhibits it (methanol/ethylene glycol poisoning).
Condition cards:Methanol poisoning →Ethylene glycol (antifreeze) poisoning →
Made from Ethanol by MEOS — CYP2E1 (smooth ER)
MEOS — CYP2E1 (smooth ER) — Ethanol metabolism
Cofactors: NADPH + O₂
Induced by chronic drinking; makes ROS; also converts acetaminophen → NAPQI → hepatic necrosis at normal doses.
Condition cards:Acetaminophen hepatotoxicity in chronic alcohol use (CYP2E1/NAPQI) →
Becomes Acetate via Aldehyde dehydrogenase (ALDH2, mitochondrial)
Aldehyde dehydrogenase (ALDH2, mitochondrial) — Ethanol metabolism
Cofactors: NAD⁺ → NADH
Inhibited by: Disulfiram; Metronidazole
Deficiency: ALDH2 polymorphism / disulfiram — acetaldehyde accumulation: flushing, headache, nausea, hypotension after drinking
ALDH2*2 (rs671, ~40% of East Asians) → acetaldehyde accumulates → flushing, nausea, tachycardia (same as disulfiram); ↑ esophageal cancer risk.
Condition cards:ALDH2 deficiency ('Asian flush', rs671) →Disulfiram (Antabuse) - acetaldehyde reaction →
Becomes ↑ NADH / NAD⁺ ratio via Net: 2 NADH per ethanol
Net: 2 NADH per ethanol — Ethanol metabolism
One from ADH, one from ALDH — the redox shift behind every downstream consequence.