Most of the alcohol (ethyl alcohol) that we are taking in when we drink is being completely oxidized to carboxylic acid. However, some of it goes into other parts and being excreted. Oxidation of ethanol may not be complete thus can be oxidized into ethanal (an aldehyde) which is toxic to our body at significant concentrations. This oxidation is being catalysed by a cytosolic enzyme alcohol dehydrogenase (ADH). The equation for this reaction is:
`CH_3CH_2OH + NAD^+ -> CH_3CHO + NADH + H^+`
`CH_3CH_2OH` -> ethanol
`CH_3CHO` -> ethanal
`NAD` -> Nicotinamide adenine dinucleotide
Ethanal (acetaldehyde) is a probable carcinogen and is known to damage the liver thus preventing it from doing its biological functions in the human body. Ethanal binds to protein molecules to form adducts and eventually lead to formation of organ disease.