Functions of cell organelles MCQs With Answer is a focused resource for B.Pharm students to master cellular organelle roles relevant to pharmacology, drug metabolism and therapeutic targeting. This concise, keyword-rich introduction covers organelles such as mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, ribosomes and plasma membrane with emphasis on biochemical functions, drug-processing enzymes (e.g., CYP450), intracellular trafficking and implications for drug action and toxicity. Questions reinforce concepts like ATP synthesis, protein folding, glycosylation, autophagy and membrane transport that are critical for understanding pharmacokinetics and pharmacodynamics. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which organelle is the primary site of oxidative phosphorylation and ATP production in eukaryotic cells?
- Mitochondrion
- Golgi apparatus
- Ribosome
- Endoplasmic reticulum
Correct Answer: Mitochondrion
Q2. Where are membrane-bound cytochrome P450 enzymes, important for drug metabolism, primarily located?
- Smooth endoplasmic reticulum
- Lysosome
- Peroxisome
- Mitochondrial matrix
Correct Answer: Smooth endoplasmic reticulum
Q3. Which organelle is chiefly responsible for post-translational modification and sorting of proteins, including glycosylation?
- Golgi apparatus
- Nucleus
- Ribosome
- Peroxisome
Correct Answer: Golgi apparatus
Q4. Ribosomes are the cellular sites for which of the following processes?
- Protein synthesis (translation)
- Lipid synthesis
- DNA replication
- ATP production
Correct Answer: Protein synthesis (translation)
Q5. Lysosomes are best known for which cellular function relevant to drug degradation?
- Intracellular digestion of macromolecules and autophagy
- ATP synthesis
- Protein translation
- DNA transcription
Correct Answer: Intracellular digestion of macromolecules and autophagy
Q6. Peroxisomes play a crucial role in which metabolic pathway affecting drug metabolism and toxicity?
- Beta-oxidation of very-long-chain fatty acids and detoxification of hydrogen peroxide
- Oxidative phosphorylation
- Protein glycosylation
- mRNA splicing
Correct Answer: Beta-oxidation of very-long-chain fatty acids and detoxification of hydrogen peroxide
Q7. The rough endoplasmic reticulum (RER) is distinct from the smooth ER because it is studded with which structures?
- Ribosomes
- Peroxisomes
- Lysosomal enzymes
- Transport vesicles only
Correct Answer: Ribosomes
Q8. Which organelle contains hydrolytic enzymes active at acidic pH and is involved in receptor-mediated endocytosis?
- Lysosome
- Golgi apparatus
- Endoplasmic reticulum
- Ribosome
Correct Answer: Lysosome
Q9. Proteasomes are primarily responsible for which cellular process important for regulating protein levels?
- Ubiquitin-mediated protein degradation
- Lipid synthesis
- Glycosylation of secreted proteins
- DNA repair
Correct Answer: Ubiquitin-mediated protein degradation
Q10. Which organelle is the major site of lipid synthesis and steroid hormone biosynthesis relevant to pharmacology?
- Smooth endoplasmic reticulum
- Mitochondrion
- Golgi apparatus
- Lysosome
Correct Answer: Smooth endoplasmic reticulum
Q11. The nuclear pore complex primarily facilitates which process?
- Selective transport of RNA and proteins between nucleus and cytoplasm
- Mitochondrial ATP export
- Protein glycosylation
- Lipid droplet formation
Correct Answer: Selective transport of RNA and proteins between nucleus and cytoplasm
Q12. Which organelle is the main site for synthesis of secretory and membrane proteins?
- Rough endoplasmic reticulum
- Peroxisome
- Golgi apparatus
- Mitochondrion
Correct Answer: Rough endoplasmic reticulum
Q13. Autophagy involves sequestration of cytoplasmic material into vesicles that fuse with which organelle for degradation?
- Lysosome
- Golgi apparatus
- Endoplasmic reticulum
- Ribosome
Correct Answer: Lysosome
Q14. Which organelle maintains intracellular calcium storage and contributes to calcium-dependent signaling?
- Sarcoplasmic/endoplasmic reticulum
- Golgi apparatus
- Peroxisome
- Ribosome
Correct Answer: Sarcoplasmic/endoplasmic reticulum
Q15. The Golgi apparatus packages proteins into vesicles for which of the following destinations?
- Secretion, plasma membrane insertion, or lysosomes
- Mitochondrial matrix only
- Nuclear import only
- Cytosolic proteasomes only
Correct Answer: Secretion, plasma membrane insertion, or lysosomes
Q16. Which cytoskeletal element forms microtubules that are essential for vesicular transport and mitotic spindle formation?
- Tubulin (microtubules)
- Actin filaments
- Intermediate filaments
- Myosin fibers
Correct Answer: Tubulin (microtubules)
Q17. Which organelle is involved in the detoxification of reactive oxygen species using catalase?
- Peroxisome
- Lysosome
- Mitochondrion
- Golgi apparatus
Correct Answer: Peroxisome
Q18. Signal peptides direct newly synthesized proteins to which organelle for secretion or membrane insertion?
- Rough endoplasmic reticulum
- Mitochondrion
- Peroxisome
- Proteasome
Correct Answer: Rough endoplasmic reticulum
Q19. Mitochondrial permeability transition pore opening is most directly associated with which cellular event?
- Apoptosis and cell death
- Protein glycosylation
- Autophagosome formation
- mRNA translation
Correct Answer: Apoptosis and cell death
Q20. Which organelle synthesizes most of the cell’s membrane phospholipids?
- Endoplasmic reticulum
- Golgi apparatus
- Mitochondrion
- Ribosome
Correct Answer: Endoplasmic reticulum
Q21. The glycocalyx at the plasma membrane is composed of which macromolecules that influence drug–cell interactions?
- Glycoproteins and glycolipids
- Phospholipids only
- DNA and RNA
- Ribosomal proteins
Correct Answer: Glycoproteins and glycolipids
Q22. Which organelle is directly involved in antigen presentation via MHC class II processing pathway?
- Lysosome (endosomal/lysosomal compartments)
- Golgi apparatus
- Rough endoplasmic reticulum only
- Peroxisome
Correct Answer: Lysosome (endosomal/lysosomal compartments)
Q23. The mitochondrial electron transport chain complexes are located in which mitochondrial region?
- Inner mitochondrial membrane
- Outer mitochondrial membrane
- Mitochondrial matrix only
- Intermembrane space only
Correct Answer: Inner mitochondrial membrane
Q24. Which organelle is essential for N-linked glycosylation initiation of proteins?
- Rough endoplasmic reticulum
- Golgi apparatus
- Mitochondrion
- Peroxisome
Correct Answer: Rough endoplasmic reticulum
Q25. Endocytosed ligands destined for degradation are delivered to which organelle following early and late endosome maturation?
- Lysosome
- Golgi apparatus
- Endoplasmic reticulum
- Peroxisome
Correct Answer: Lysosome
Q26. Which organelle contributes to xenobiotic conjugation reactions through enzymes like UDP-glucuronosyltransferases?
- Smooth endoplasmic reticulum
- Golgi apparatus
- Peroxisome
- Mitochondrion
Correct Answer: Smooth endoplasmic reticulum
Q27. Microfilaments composed of actin are primarily responsible for which cellular function?
- Cell shape, motility and muscle contraction
- Vesicle formation in Golgi
- ATP production
- DNA replication
Correct Answer: Cell shape, motility and muscle contraction
Q28. Which organelle synthesizes mitochondrial proteins encoded by mitochondrial DNA?
- Mitochondrial ribosomes (mitoribosomes)
- Cytosolic ribosomes only
- Rough endoplasmic reticulum
- Golgi apparatus
Correct Answer: Mitochondrial ribosomes (mitoribosomes)
Q29. Which organelle is central to the unfolded protein response when misfolded proteins accumulate?
- Endoplasmic reticulum
- Lysosome
- Mitochondrion
- Ribosome
Correct Answer: Endoplasmic reticulum
Q30. Secretory vesicles packaged by the Golgi typically require which cytoskeletal tracks for directed transport?
- Microtubules and motor proteins (kinesin/dynein)
- Intermediate filaments only
- Actin filaments exclusively
- Ribosomal tracks
Correct Answer: Microtubules and motor proteins (kinesin/dynein)
Q31. Which organelle is the primary site for synthesis of selenoproteins involved in antioxidant defense?
- Rough endoplasmic reticulum and cytosolic translation machinery
- Golgi apparatus
- Peroxisome only
- Mitochondrion only
Correct Answer: Rough endoplasmic reticulum and cytosolic translation machinery
Q32. The centrosome in animal cells functions mainly as which of the following?
- Microtubule-organizing center for mitosis
- Primary site of ATP synthesis
- Major site of lipid storage
- Protein glycosylation center
Correct Answer: Microtubule-organizing center for mitosis
Q33. Which organelle harbors enzymes for the synthesis and breakdown of cholesterol and is relevant to statin pharmacology?
- Smooth endoplasmic reticulum
- Peroxisome
- Mitochondrion
- Lysosome
Correct Answer: Smooth endoplasmic reticulum
Q34. Which organelle’s dysfunction is directly implicated in lysosomal storage diseases like Tay–Sachs?
- Lysosome
- Golgi apparatus
- Peroxisome
- Endoplasmic reticulum
Correct Answer: Lysosome
Q35. Which organelle is primarily responsible for assembling ribosomal subunits from rRNA and proteins?
- Nucleolus
- Nuclear envelope
- Golgi apparatus
- Peroxisome
Correct Answer: Nucleolus
Q36. Drugs that disrupt microtubule dynamics (e.g., colchicine) most directly affect which organelle-associated processes?
- Vesicular transport and mitotic spindle formation
- Protein glycosylation in Golgi only
- ATP synthesis in mitochondria only
- Peroxisomal beta-oxidation only
Correct Answer: Vesicular transport and mitotic spindle formation
Q37. Which organelle surface contains receptors and enzymes for endocytosis such as clathrin-mediated uptake?
- Plasma membrane (with coated pits)
- Mitochondrial membrane
- Golgi cisterna
- Peroxisomal membrane
Correct Answer: Plasma membrane (with coated pits)
Q38. Which organelle helps maintain cellular osmotic balance and stores ions and metabolites in plant cells (less prominent in animal cells)?
- Vacuole
- Golgi apparatus
- Lysosome
- Peroxisome
Correct Answer: Vacuole
Q39. Which organelle contains enzymes that perform oxidative deamination and produce hydrogen peroxide as a by-product?
- Peroxisome
- Mitochondrion
- Lysosome
- Golgi apparatus
Correct Answer: Peroxisome
Q40. Post-translational addition of mannose-6-phosphate targets enzymes to which organelle?
- Lysosome
- Golgi apparatus
- Endoplasmic reticulum
- Proteasome
Correct Answer: Lysosome
Q41. Which organelle is the first to receive secretory proteins from the RER for further processing?
- Golgi apparatus (cis face)
- Plasma membrane
- Mitochondrion
- Peroxisome
Correct Answer: Golgi apparatus (cis face)
Q42. Which organelle contains proton pumps that acidify its lumen to activate hydrolases?
- Lysosome
- Golgi apparatus
- Endoplasmic reticulum
- Peroxisome
Correct Answer: Lysosome
Q43. Which organelle is primarily involved in synthesis of mitochondrial membrane proteins encoded by nuclear DNA?
- Rough endoplasmic reticulum and cytosolic ribosomes with targeting signals
- Golgi apparatus only
- Peroxisome only
- Nucleolus only
Correct Answer: Rough endoplasmic reticulum and cytosolic ribosomes with targeting signals
Q44. Which organelle plays a role in calcium-dependent exocytosis of neurotransmitters at synapses?
- Synaptic vesicles derived from Golgi/plasma membrane trafficking
- Peroxisomes
- Mitochondrial matrix
- Nucleus
Correct Answer: Synaptic vesicles derived from Golgi/plasma membrane trafficking
Q45. Which organelle is a crucial pharmacological target in cancer using proteasome inhibitors like bortezomib?
- Proteasome in the cytosol and nucleus
- Lysosome only
- Golgi apparatus only
- Peroxisome only
Correct Answer: Proteasome in the cytosol and nucleus
Q46. Lipid rafts in the plasma membrane are enriched in which components and influence drug receptor localization?
- Cholesterol and sphingolipids
- Cardiolipin only
- DNA and histones
- Ribosomal proteins
Correct Answer: Cholesterol and sphingolipids
Q47. Which organelle is responsible for trimming and complex glycan formation during secretory protein maturation?
- Golgi apparatus (medial and trans cisternae)
- Rough endoplasmic reticulum only
- Mitochondrion
- Peroxisome
Correct Answer: Golgi apparatus (medial and trans cisternae)
Q48. Which organelle’s dysfunction leads to accumulation of very long chain fatty acids as seen in Zellweger syndrome?
- Peroxisome
- Mitochondrion
- Golgi apparatus
- Lysosome
Correct Answer: Peroxisome
Q49. Which organelle actively maintains membrane asymmetry and contains flippases and floppases?
- Plasma membrane
- Golgi apparatus
- Endoplasmic reticulum only
- Mitochondrion
Correct Answer: Plasma membrane
Q50. Which organelle is central to intrinsic apoptosis by releasing cytochrome c into the cytosol?
- Mitochondrion
- Lysosome
- Endoplasmic reticulum
- Golgi apparatus
Correct Answer: Mitochondrion
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