What substance is broken down by the enzyme aldehyde dehydrogenase?

The substance that is broken down by the enzyme aldehyde dehydrogenase is acetaldehyde. This enzyme is crucial in the metabolic pathway for alcohol, specifically in the process of converting acetaldehyde, a toxic by-product of ethanol metabolism, into acetic acid, which is less harmful and can then be further metabolized for energy or eliminated from the body.

Ethanol is the alcohol consumed, and it's first metabolized to acetaldehyde by alcohol dehydrogenase before being processed by aldehyde dehydrogenase. Conversely, the choices referring to alcohol itself and carbon dioxide do not accurately identify the substrate for aldehyde dehydrogenase. Alcohol does not directly undergo breakdown by this enzyme; instead, it is first transformed into acetaldehyde. Carbon dioxide, on the other hand, is a by-product of various metabolic processes including the oxidation of acetic acid but is not the substrate for aldehyde dehydrogenase. This highlights the specificity of the enzyme's activity in the detoxification pathway that manages the by-products of alcohol consumption.