Q34. In hepatocytes, the detoxification of drugs occurs in ______
(A) Golgi apparatus
(B) Nucleolus
(C) Rough endoplasmic reticulum
(D) Smooth endoplasmic reticulum
Smooth endoplasmic reticulum is the site of drug detoxification in hepatocytes due to its abundance of cytochrome P450 enzymes.
Option Analysis
Golgi apparatus: Modifies, sorts, and packages proteins and lipids for secretion or use within the cell, but lacks enzymes for drug metabolism.
Nucleolus: Site of ribosomal RNA synthesis and ribosome assembly within the nucleus; unrelated to detoxification processes.
Rough endoplasmic reticulum: Studded with ribosomes, it specializes in protein synthesis and folding, not xenobiotic metabolism.
Smooth endoplasmic reticulum: Houses cytochrome P450 enzymes for phase I oxidation of lipophilic drugs into water-soluble forms, enabling excretion; most abundant organelle in hepatocytes.
Correct Answer
(D) Smooth endoplasmic reticulum.
Introduction
Drug detoxification in hepatocytes is a critical liver function, primarily occurring in the smooth endoplasmic reticulum (SER). This process protects the body from toxins through phase I and II metabolism, making it essential knowledge for CSIR NET Life Sciences aspirants studying hepatocyte detoxification.
Hepatocyte Detoxification Mechanism
Hepatocytes receive blood from the portal vein and hepatic artery, exposing them to drugs and toxins. The smooth endoplasmic reticulum performs phase I reactions, where cytochrome P450 enzymes oxidize lipophilic compounds into hydrophilic metabolites for easier excretion. Phase II involves conjugation in the same region, enhancing solubility.
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Cytochrome P450 family (e.g., CYP3A4) metabolizes ~50% of drugs.
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Flavin monooxygenases (FMOs) and glutathione S-transferases (GSTs) assist in detoxification.
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Transporters like ABC and SLC facilitate metabolite export via bile.
Why Smooth ER in Hepatocytes?
Unlike rough ER for protein synthesis, SER lacks ribosomes and specializes in lipid metabolism and detoxification. Liver cells proliferate SER in response to chronic exposure, such as alcohol, boosting enzyme activity. This adaptation underscores hepatocytes’ role in homeostasis.
Exam Relevance for CSIR NET
Questions on hepatocyte detoxification test cell biology and biochemistry integration. Differentiate SER from other organelles: Golgi for packaging, nucleolus for ribosomes, rough ER for translation. Master cytochrome P450 induction for competitive edges.
