USMLE

Ethanol Metabolism

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Biochemical Pathways
  1. Glycolysis
  2. Cori Cycle
  3. De Novo Purine Synthesis
  4. De Novo Pyrimidine Synthesis
  5. Purine Salvage
  6. Purine Excretion
  7. Ethanol Metabolism
  8. Pyruvate Metabolism
  9. HMP Shunt (Pentose Phosphate Pathway)
  10. Galactose Metabolism
  11. Sorbitol (Polyol) Pathway
  12. Urea Cycle
  13. Alanine (Cahill) Cycle
  14. Catecholamine Synthesis & Breakdown
  15. Homocysteine Metabolism
  16. Fatty Acid Synthesis (Citrate Shuttle)
  17. Fatty Acid Breakdown (Carnitine Shuttle)
  18. Propionic Acid Pathway

Alcohol or Ethanol Metabolism occurs in the liver through several steps, beginning with ethanol (alcohol), proceeding through acetaldehyde, and ending with acetate (acetic acid), which is excreted in the urine.

First, ethanol can be metabolized into acetaldehyde in 3 ways. The most important way is through alcohol dehydrogenase in the cytoplasm, which is blocked by the drug, fomepizole. Alcohol dehydrogenase operates via zero-order kinetics, which means that it operates at a constant rate regardless of how much alcohol is present (amount ingested). Less important enzymes include CYP2E1 in the microsome, or catalase in the peroxisome.

The acetaldehyde is then metabolized into acetate through the actions of aldehyde dehydrogenase. The drug disulfiram is given to discourage drinking, as it blocks aldehdye dehydrogenase and leads to the build-up of the toxic intermediate: acetaldehyde.

The metabolism of alcohol usually generates 2 molecules of NADH from NAD+, which increases the NADH to NAD+ ratio. The increase in this ratio leads to a number clinical findings, such as lactic acidosis, fasting hypoglycemia, hepatosteatosis, and ketogenesis.

Find Ethanol Metabolism and more Biochemical Pathways among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.