Liver Systems

"The liver metabolizes up to 85%–98% of the circulatory ethanol. The liver uses two metabolic processes to get rid of this circulatory ethanol as quickly and safely as possible: the alcohol dehydrogenase system and the microsomal ethanol oxidizing system, or MEOS. About 80 to 90% of the total hepatic ethanol uptake is processed via the alcohol dehydrogenase system. The degradation of ethanol begins in the liver. The enzyme that catalyzes this reaction is called alcohol dehydrogenase. The products from this reaction are acetaldehyde, NADH, a reduced coenzyme that carries electrons from one reaction to another, and H+ ion. Acetaldehyde is very toxic to the liver and the body’s cells. The moment acetaldehyde is produced, it must be degraded to protect the liver cells. Acetaldehyde dehydrogenase, or ALDH, converts acetaldehyde into acetate, a non-toxic molecule. In a moderate drinker, about 10 to 20% of the total liver ethanol uptake is processed via the microsomal ethanol oxidizing system. During periods of heavy drinking, the MEOS system will metabolize most of the excess ethanol ingested. Heavy drinking stimulates the human body to include the MEOS system enzymes to clear ethanol faster from the body. The MEOS system is also located in the liver. Similar to the alcohol dehydrogenase system, acetaldehyde dehydrogenase will immediately convert acetaldehyde into acetate, a non-toxic molecule. Other products from this reaction are NADH and H+ ion."