The options below show the reactants, products, and enzymes involved in alcohol metabolism. Reactions are indicated with arrows, with the enzymes that catalyze those reactions written in italics. Which option indicates the correct order for alcohol metabolism in the body?

• A. Alcohol → ADH → Acetate → ALDH → Usable calories.
• B. Methanol → ALDH → Acetaldehyde → ADH → Usable calories.
• C. Alcohol → ALDH → Acetate → ADH → Acetaldehyde.
• D. Ethanol → ADH → Acetaldehyde → ALDH → Acetate.

Answer: (D)

Verified step by step guidance

1. Understand that alcohol metabolism primarily involves the conversion of ethanol (the type of alcohol found in beverages) into substances that the body can further process for energy or elimination.
2. Identify the first step: ethanol is converted into acetaldehyde by the enzyme alcohol dehydrogenase (ADH). This is a crucial step because acetaldehyde is a toxic intermediate.
3. Recognize the second step: acetaldehyde is then converted into acetate by the enzyme aldehyde dehydrogenase (ALDH). This step reduces toxicity by transforming acetaldehyde into a less harmful compound.
4. Note that acetate can be further metabolized into acetyl-CoA, which enters the citric acid cycle to produce usable energy (calories) for the body.
5. Therefore, the correct order of alcohol metabolism is: Ethanol → (ADH) → Acetaldehyde → (ALDH) → Acetate, which aligns with the final option provided.