Ethanol \(\left(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\right)\) is consumed in alcoholic beverages, but another alcohol, methanol (CH \(_{4} \mathrm{O}\) ), is toxic. What explanation can you give for this?

When ethanol (C2H6O) is consumed, it is primarily metabolized by the liver. The following simplified steps occur in the metabolic process: 1. Ethanol is first converted to acetaldehyde by the enzyme alcohol dehydrogenase (ADH). 2. Acetaldehyde is then converted to acetate by the enzyme aldehyde dehydrogenase (ALDH). 3. Lastly, acetate is converted into carbon dioxide and water. While ethanol metabolism results in relatively harmless byproducts, methanol metabolism follows a different pathway, leading to toxic metabolites.

Methanol (CH4O) is metabolized in the liver, primarily by the same enzymes which metabolize ethanol - alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). The main difference arises in the products formed during the metabolism: 1. Methanol is first converted to formaldehyde by the enzyme alcohol dehydrogenase (ADH). 2. Formaldehyde is then converted to formic acid by the enzyme aldehyde dehydrogenase (ALDH). The metabolism process of methanol generates toxic byproducts: formaldehyde and formic acid.

Formaldehyde is a well-known toxic substance, causing irritation and damage to cells. This can lead to a range of symptoms like dizziness, headache, and even severe cases like vision damage or blindness. Formic acid, on the other hand, inhibits the action of cytochrome c oxidase in the electron transport chain (ETC) of mitochondria. This leads to a disruption in cellular respiration, energy production, and the accumulation of lactic acid, which causes metabolic acidosis.

As mentioned earlier, both methanol and ethanol share the same enzymes for metabolism in the liver: alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). When ethanol is present in the body, it competes with methanol for these enzymes. Thus, by consuming ethanol, methanol's metabolism is slowed down, which delays the formation of its toxic metabolites, namely, formaldehyde and formic acid. In conclusion: Ethanol (C2H6O) is consumed in alcoholic beverages and is less toxic than methanol (CH4O), primarily because the byproducts (acetaldehyde and acetate) formed during its metabolism are less harmful than those formed during the metabolism of methanol (formaldehyde and formic acid). Furthermore, the presence of ethanol in the body can help minimize the toxic effects of methanol by delaying its metabolism.