Question

The main toxic metabolite of alcohol which is responsible for alcohol related injury to different organs is :

• A. \( \text{Formaldehyde} \)
• B. \( \text{Cysteamine} \)
• C. \( \text{Acetaldehyde} \)
• D. \( \text{Malondialdehyde} \)

Hint:

\textbf{Biochemistry: Alcohol Metabolism.} Remember the two main enzymes involved in ethanol metabolism: alcohol dehydrogenase (ethanol to acetaldehyde) and aldehyde dehydrogenase (acetaldehyde to acetate). Acetaldehyde is the key intermediate responsible for much of alcohol's toxicity.

Answer 1

The Correct Option is C

When alcohol (ethanol) is ingested, it undergoes metabolism primarily in the liver through a series of enzymatic reactions. The first major step in this process is the oxidation of ethanol to acetaldehyde by the enzyme alcohol dehydrogenase. Acetaldehyde is a highly reactive and toxic compound that is responsible for many of the harmful effects of alcohol on various organs in the body. Acetaldehyde can: Damage DNA and proteins. Interfere with enzyme function. Promote inflammation and oxidative stress. Contribute to liver damage (alcoholic hepatitis, cirrhosis). Play a role in alcohol-related cancers. Cause some of the immediate effects of alcohol consumption, such as flushing and nausea (especially in individuals with aldehyde dehydrogenase deficiency). Acetaldehyde is subsequently metabolized to acetate (a less toxic compound) by the enzyme aldehyde dehydrogenase. However, the accumulation of acetaldehyde due to excessive alcohol consumption or impaired aldehyde dehydrogenase activity leads to significant cellular damage. Let's briefly look at the other options: Formaldehyde: While formaldehyde is a toxic aldehyde, it is not the primary direct metabolite of ethanol in the body. It can be formed during the metabolism of methanol, another type of alcohol. Cysteamine: This is an aminothiol compound with various pharmacological effects, including as a treatment for cystinosis. It is not a metabolite of alcohol. Malondialdehyde: This is a product of lipid peroxidation, a process that can be induced by alcohol consumption and acetaldehyde, contributing to oxidative damage. However, it is a secondary product of alcohol-related injury, not the primary toxic metabolite. Therefore, acetaldehyde is the main toxic metabolite of alcohol responsible for alcohol-related injury to different organs.