Eukaryotes – introduction MCQs With Answer: This concise, student-focused introduction explains eukaryotic cell structure, organelles, and key processes relevant to B. Pharm courses. Learn about the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, cytoskeleton, membrane transport, signal transduction, and differences from prokaryotes—topics essential for pharmacology, drug targeting, and cellular physiology. Emphasis is on organelle functions, protein trafficking, drug-metabolizing enzymes (like cytochrome P450), and clinical relevance such as antifungal targets and multidrug resistance. Simple diagrams and MCQs reinforce concepts and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which organelle houses the cell’s genetic material and controls transcription in eukaryotic cells?
- Nucleus
- Mitochondrion
- Golgi apparatus
- Ribosome
Correct Answer: Nucleus
Q2. Which structure is primarily responsible for ATP production via oxidative phosphorylation?
- Endoplasmic reticulum
- Mitochondrion
- Lysosome
- Peroxisome
Correct Answer: Mitochondrion
Q3. Which ribosomal size is typical for eukaryotic cytosolic ribosomes?
- 70S
- 50S
- 80S
- 30S
Correct Answer: 80S
Q4. Which organelle is the main site of protein glycosylation and post-translational modification?
- Golgi apparatus
- Peroxisome
- Ribosome
- Centrosome
Correct Answer: Golgi apparatus
Q5. The rough endoplasmic reticulum is distinguished by presence of which component?
- Lipid droplets
- Ribosomes on its cytosolic surface
- Matrix granules
- Actin filaments
Correct Answer: Ribosomes on its cytosolic surface
Q6. Which signal directs a nascent polypeptide to the endoplasmic reticulum?
- Nuclear localization signal
- Mitochondrial targeting sequence
- ER signal peptide (signal sequence)
- Peroxisomal targeting signal
Correct Answer: ER signal peptide (signal sequence)
Q7. Which cellular process involves engulfment of extracellular material by membrane invagination forming vesicles?
- Exocytosis
- Endocytosis
- Apoptosis
- Autophagy
Correct Answer: Endocytosis
Q8. Which organelle contains hydrolytic enzymes for intracellular digestion?
- Lysosome
- Golgi apparatus
- Ribosome
- Centrosome
Correct Answer: Lysosome
Q9. Which eukaryotic organelle is central to lipid synthesis and drug metabolism (including cytochrome P450 enzymes)?
- Smooth endoplasmic reticulum
- Rough endoplasmic reticulum
- Mitochondrion
- Peroxisome
Correct Answer: Smooth endoplasmic reticulum
Q10. Which cytoskeletal component is mainly responsible for muscle contraction and cell shape changes?
- Microtubules
- Intermediate filaments
- Microfilaments (actin)
- Keratins
Correct Answer: Microfilaments (actin)
Q11. Which structure organizes microtubules and is important for mitotic spindle formation in animal cells?
- Nucleolus
- Centrosome (containing centrioles)
- Golgi apparatus
- Peroxisome
Correct Answer: Centrosome (containing centrioles)
Q12. Eukaryotic chromosomes are packaged with which proteins to form chromatin?
- Actins
- Histones
- Tubulins
- Integrins
Correct Answer: Histones
Q13. Which process removes introns from pre-mRNA in the nucleus?
- Translation
- Splicing by spliceosome
- Glycosylation
- Polyadenylation
Correct Answer: Splicing by spliceosome
Q14. Which membrane lipid contributes to membrane fluidity and is a precursor for steroid synthesis?
- Phosphatidylcholine
- Sphingomyelin
- Cholesterol
- Glycolipid
Correct Answer: Cholesterol
Q15. Which transport mechanism moves molecules down their concentration gradient without energy input?
- Primary active transport
- Facilitated diffusion
- Endocytosis
- Exocytosis
Correct Answer: Facilitated diffusion
Q16. Which family of transporters is commonly associated with drug efflux and multidrug resistance in eukaryotic cells?
- SLC transporters
- ABC transporters (e.g., P-glycoprotein)
- Ionotropic receptors
- Glycosyltransferases
Correct Answer: ABC transporters (e.g., P-glycoprotein)
Q17. Which organelle is involved in reactive oxygen species detoxification and beta-oxidation of very long-chain fatty acids?
- Peroxisome
- Lysosome
- Mitochondrion
- Golgi apparatus
Correct Answer: Peroxisome
Q18. In eukaryotic cells, which process directly produces proteins from mRNA?
- Transcription
- Translation
- Replication
- Splicing
Correct Answer: Translation
Q19. Which eukaryotic receptor class activates G-proteins to mediate intracellular signaling?
- Receptor tyrosine kinases (RTKs)
- Ligand-gated ion channels
- G protein-coupled receptors (GPCRs)
- Integrins
Correct Answer: G protein-coupled receptors (GPCRs)
Q20. Which cellular compartment contains the nucleolus where ribosomal RNA is synthesized?
- Cytosol
- Nucleus
- Golgi lumen
- Endoplasmic reticulum lumen
Correct Answer: Nucleus
Q21. Which stage of the cell cycle is characterized by DNA synthesis?
- G1 phase
- S phase
- G2 phase
- M phase
Correct Answer: S phase
Q22. Cyclins and cyclin-dependent kinases (CDKs) regulate which cellular process?
- Apoptosis only
- Protein glycosylation
- Cell cycle progression
- Lipid metabolism
Correct Answer: Cell cycle progression
Q23. Which pathway triggers programmed cell death via caspase activation?
- Autophagy
- Necrosis
- Apoptosis
- Endocytosis
Correct Answer: Apoptosis
Q24. Which organelle-derived vesicle fuses with the plasma membrane to secrete proteins?
- Lysosome
- Transport vesicle from Golgi (secretory vesicle)
- Peroxisome
- Mitochondrial vesicle
Correct Answer: Transport vesicle from Golgi (secretory vesicle)
Q25. Which eukaryotic feature is absent in prokaryotes and is a key diagnostic for eukaryotic cells?
- Plasma membrane
- Nucleus with nuclear envelope
- Ribosomes
- Cell membrane transporters
Correct Answer: Nucleus with nuclear envelope
Q26. Which molecular machine synthesizes ATP using the proton gradient in mitochondria?
- ATP synthase (Complex V)
- Cytochrome c oxidase (Complex IV)
- NADH dehydrogenase (Complex I)
- Succinate dehydrogenase (Complex II)
Correct Answer: ATP synthase (Complex V)
Q27. Which eukaryotic organelle is the primary site for initial protein synthesis for secreted and membrane proteins?
- Golgi apparatus
- Rough endoplasmic reticulum
- Mitochondrion
- Peroxisome
Correct Answer: Rough endoplasmic reticulum
Q28. Which modification commonly occurs in the Golgi and affects protein folding, stability, and cell recognition?
- Ubiquitination
- Glycosylation
- Phosphorylation
- Methylation
Correct Answer: Glycosylation
Q29. Which nuclear pore function is essential for regulated import of transcription factors into the nucleus?
- Passive diffusion of proteins >60 kDa
- Active transport via nuclear localization signals (NLS)
- Export of mRNA only
- Sequestration of ribosomes
Correct Answer: Active transport via nuclear localization signals (NLS)
Q30. Which process describes degradation of cellular components through lysosomal pathways during nutrient starvation?
- Exocytosis
- Autophagy
- Endocytosis
- Necroptosis
Correct Answer: Autophagy
Q31. Which organelle contains the set of enzymes that catalyze beta-oxidation of fatty acids in many eukaryotic cells?
- Mitochondrion and peroxisome depending on chain length
- Golgi apparatus only
- Lysosome only
- Ribosome only
Correct Answer: Mitochondrion and peroxisome depending on chain length
Q32. Which cellular structure provides tracks for vesicle transport powered by motor proteins like kinesin and dynein?
- Microfilaments
- Intermediate filaments
- Microtubules
- Lipid rafts
Correct Answer: Microtubules
Q33. Which enzyme family in the smooth ER is crucial for phase I drug metabolism?
- Glycosyltransferases
- Cytochrome P450 monooxygenases
- Sulfotransferases
- UDP-glucuronosyltransferases
Correct Answer: Cytochrome P450 monooxygenases
Q34. Which cellular compartment contains DNA in mitochondria and can synthesize a subset of mitochondrial proteins?
- Nucleus
- Mitochondrial matrix
- Rough ER lumen
- Golgi lumen
Correct Answer: Mitochondrial matrix
Q35. Which cytoskeletal filaments provide tensile strength and mechanical stability to cells?
- Microtubules
- Microfilaments
- Intermediate filaments
- Myosin filaments
Correct Answer: Intermediate filaments
Q36. Which process describes vesicular transport from the ER to the Golgi apparatus?
- Retrograde transport
- Anterograde transport
- Exocytosis to extracellular space
- Endocytosis from plasma membrane
Correct Answer: Anterograde transport
Q37. Which cellular receptor type directly phosphorylates tyrosine residues on target proteins upon ligand binding?
- GPCRs
- Receptor tyrosine kinases (RTKs)
- Toll-like receptors
- Ion channels
Correct Answer: Receptor tyrosine kinases (RTKs)
Q38. Which nuclear substructure is most active during ribosome biogenesis?
- Nuclear envelope
- Nucleolus
- Chromatin rim
- Nuclear lamina
Correct Answer: Nucleolus
Q39. Which eukaryotic process ensures quality control of misfolded proteins in the ER?
- Ubiquitin-proteasome system and ER-associated degradation (ERAD)
- Autophagy only
- Mitochondrial fusion
- Lysosomal exocytosis
Correct Answer: Ubiquitin-proteasome system and ER-associated degradation (ERAD)
Q40. Which lipid modification anchors some proteins to the inner leaflet of the plasma membrane?
- Glycosylation
- Myristoylation or prenylation (lipidation)
- Phosphorylation
- Acetylation
Correct Answer: Myristoylation or prenylation (lipidation)
Q41. Which drug target exploits structural differences between fungal and human cells in eukaryotes?
- Bacterial cell wall synthesis enzymes
- Fungal ergosterol synthesis enzymes
- Mammalian histone deacetylases
- Human ribosomal RNA
Correct Answer: Fungal ergosterol synthesis enzymes
Q42. Which eukaryotic organelle is most directly involved in calcium storage and signaling in muscle cells?
- Mitochondrion
- Sarcoplasmic reticulum (specialized ER)
- Golgi apparatus
- Lysosome
Correct Answer: Sarcoplasmic reticulum (specialized ER)
Q43. Which mechanism decreases receptor responsiveness by removing receptors from the plasma membrane into endosomes?
- Receptor downregulation via endocytosis
- Increased transcription
- Translation initiation
- Peroxisomal import
Correct Answer: Receptor downregulation via endocytosis
Q44. Which process in the nucleus adds a poly(A) tail to pre-mRNA and enhances stability?
- Capping
- Polyadenylation
- Splicing
- Translation
Correct Answer: Polyadenylation
Q45. Which organelle dysfunction commonly leads to accumulation of undegraded substrates and lysosomal storage diseases?
- Golgi dysfunction
- Mitochondrial dysfunction
- Lysosomal dysfunction
- Ribosomal dysfunction
Correct Answer: Lysosomal dysfunction
Q46. Which ion gradient directly drives ATP synthesis in mitochondria?
- Sodium gradient across plasma membrane
- Proton (H+) gradient across inner mitochondrial membrane
- Calcium gradient in cytosol
- Chloride gradient across lysosomal membrane
Correct Answer: Proton (H+) gradient across inner mitochondrial membrane
Q47. Which process transports misfolded ER proteins to the cytosol for proteasomal degradation?
- ER-associated degradation (ERAD)
- Autophagy
- Mitochondrial import
- Endocytosis
Correct Answer: ER-associated degradation (ERAD)
Q48. Which eukaryotic structure forms the mitotic spindle that separates chromosomes during mitosis?
- Actin cortex
- Microtubules radiating from centrosomes
- Intermediate filament network
- Golgi ribbons
Correct Answer: Microtubules radiating from centrosomes
Q49. Which protein complex adds ubiquitin to proteins marking them for proteasomal degradation?
- Ribosome
- Ubiquitin ligase (E3) complex
- ATP synthase
- Spliceosome
Correct Answer: Ubiquitin ligase (E3) complex
Q50. Which cellular feature in eukaryotes allows compartmentalization of metabolic pathways and increases efficiency?
- Single membrane only
- Presence of membrane-bound organelles
- Absence of cytoskeleton
- Continuous genome without chromatin
Correct Answer: Presence of membrane-bound organelles
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