COMPETITIVE EXAM MCQs SERIES of LIFE SCIENCES for UGC-CSIR NET/JRF, SLET, GATE, and other entrance tests – CELLULAR ORGANIZATION – Organisation and Function of Intracellular Organelles.
Syllabus Outline
- Cell wall, nucleus, mitochondria, Golgi bodies, lysosomes, endoplasmic reticulum, peroxisomes, plastids, vacuoles and chloroplasts.
- Structure & function of the cytoskeleton and its role in motility.
This quiz contains concept-based, most frequently asked 25 MCQs of “CELLULAR ORGANIZATION – Organisation and Function of Intracellular Organelles”. Each question has a single correct/most appropriate answer.
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1. The “GTP Cap” of a microtubule is located at:
A) The Minus end.
B) The Plus end.
C) Both Plus and Minus end.
D) The centrosome.
2. Which function is NOT performed by the Signal Recognition Particle?
A) Binding to the signal sequence.
B) Pausing translation.
C) Targeting the ribosome to the ER.
D) Cleaving the signal peptide.
3. Which cytoskeletal element moves the Cellulose Synthase Complex?
A) Actin filaments.
B) Cortical Microtubules.
C) Intermediate filaments.
D) Exocytosis force.
4. Peroxisomes import proteins in which state?
A) Unfolded linear chains.
B) Bound to Hsp70.
C) Co-translationally.
D) Fully folded and oligomeric states.
5. The drug Nocodazole affects the cell cycle by:
A) Inhibiting DNA polymerase.
B) Depolymerising microtubules.
C) Stabilising actin filaments.
D) Blocking S-phase entry.
6. A researcher injects a non-hydrolyzable analogue of GTP into the cytoplasm of a cultured cell and monitors the transport of a protein containing a classic Nuclear Localisation Signal (NLS). What is the expected outcome?
A) Nuclear import proceeds normally, but export is blocked.
B) The Importin-cargo complex enters the nucleus, but the cargo cannot be released.
C) Nuclear import is inhibited
D) The NLS-cargo accumulates at the nuclear pore complex but cannot translocate.
7. The disassembly of the nuclear envelope marks the transition from Prophase to Prometaphase. Which kinase-substrate relationship correctly initiates this process?
A) PKC phosphorylates Nup98.
B) Aurora B phosphorylates Lamin B.
C) Cyclin B-CDK1 phosphorylates Lamin A.
D) Wee1 phosphorylates Lamin A.
8. The “Exportomer” in peroxisomal protein transport refers to:
A) The export of proteases from the peroxisome.
B) The extraction of the Pex5 receptor from the peroxisomal membrane.
C) The transport of mRNA out of the peroxisome.
D) The release of acetyl-CoA to the mitochondria.
9. Consider a plant mutant defective in the Pex7 gene. What is the predicted phenotype regarding protein sorting?
A) Failure to import all peroxisomal proteins.
B) Failure to import proteins containing the C-terminal SKL motif.
C) Failure to import proteins containing the N-terminal PTS2 motif.
D) Accumulation of empty peroxisomes.
10. In a “Pulse-Chase” experiment, a secreted protein is detected in the ER and Golgi but never appears in the medium and remains Endo-H sensitive. According to the Schekman classification, this mutant belongs to:
A) Class A
B) Class B
C) Class C
D) Class D
11. The lipid anchor essential for the conjugation of Microtubule-Associated Protein 1 Light Chain 3 to the autophagosome membrane is:
A) Phosphatidylinositol-3-phosphate.
B) Phosphatidylethanolamine.
C) Cardiolipin.
D) Sphingomyelin.
12. In the “Stochastic Cap” model of microtubule dynamics, catastrophe is triggered by:
A) Complete hydrolysis of GTP in the terminal dimer.
B) Binding of Kinesin-13.
C) Loss of the GTP-tubulin cap.
D) Dephosphorylation of MAPs.
13. An actin polymerisation assay is conducted with 0.4 µM G-actin. If the critical concentration at the (+) end is 0.1 µM and at the (–) end is 0.6 µM, what will be the kinetic state of the filaments?
A) Growth at the (+) end and Shrinkage at the (–) end
B) Growth at both ends
C) Shrinkage at both ends
D) Shrinkage at the (+) end and Growth at the (–) end
14. Which drug binds F-actin filaments and prevents their depolymerisation, often used to visualise the cytoskeleton?
A) Cytochalasin D
B) Latrunculin A
C) Phalloidin
D) Nocodazole
15. Listeria monocytogenes moves inside host cells by activating which host protein complex?
A) Dynein-Dynactin
B) Arp2/3 complex
C) Formin complex
D) Myosin II
16. Which statement best describes the development of the Phragmoplast?
A) It constricts inward using an actin-myosin ring.
B) It expands centrifugally using a microtubule array to guide vesicle fusion.
C) It forms solely by endoplasmic reticulum fusion.
D) It relies on the breakdown of the nuclear envelope.
17. Monensin primarily affects the secretory pathway by:
A) Blocking ER-to-Golgi transport.
B) Neutralising the pH of the Trans-Golgi Network.
C) Inhibiting protein synthesis.
D) Dissolving the nuclear envelope.
18. Intermediate filaments differ from actin filaments and microtubules in that:
A) They possess structural polarity.
B) They require nucleotide binding and hydrolysis.
C) They serve as tracks for kinesin-based transport.
D) Their assembly depends on coiled-coil interactions without nucleotide use.
19. Taxol blocks cell division by:
A) Preventing microtubule polymerisation.
B) Preventing dynamic disassembly.
C) Inhibiting centrosome duplication.
D) Degrading Cyclin B.
20. A “Class E” yeast secretion mutant is characterised by:
A) Cytosolic vesicle accumulation.
B) An exaggerated Pre-Vacuolar Compartment.
C) ER accumulation.
D) Secretion of all vacuolar proteins.
21. Regarding the mitochondrial genome (mtDNA) and its organisation, which of the following statements shows a key difference between human and plant mitochondrial genetics?
I – Human mtDNA contains introns, whereas plant mtDNA is compact and intron-less.
II – Plant mtDNA is significantly larger than human mtDNA.
III – Plant mtDNA is characterised by frequent recombination and sub-stoichiometric molecules, whereas human mtDNA is stable.
IV – The D-loop region is absent in plant mitochondria, whereas the D-loop is well developed in human mitochondria.
A) I and II only
B) II and III only
C) III and IV only
D) I, II, III and IV
22. Chloroplast transit peptides differ from mitochondrial targeting signals primarily in that:
I – Transit peptides are enriched in hydroxylated amino acids, while mitochondrial targeting signals are rich in basic amino acids, forming amphipathic helices.
II – Transit peptides are C-terminal, while mitochondrial targeting signals are N-terminal.
III – Transit peptides are never cleaved, whereas mitochondrial targeting signals helices are cleaved
IV – Transit peptides are highly acidic, whereas mitochondrial targeting signals helices are highly basic
A) I only
B) I and II
C) II, III, and IV
D) I, II, III and IV
23. In the context of mitochondrial protein import, which of the following observations would specifically indicate a defect in the TIM22 complex rather than the TIM23 complex?
I – Failure to import the ADP/ATP carrier protein
II – Matrix enzymes, like Citrate Synthase, are normally imported.
III – Accumulation of precursor proteins with cleavable N-terminal signals in the matrix.
IV – Inhibition of import by the addition of a non-hydrolyzable ATP analogue.
V – Loss of outer membrane integrity.
A) I and II
B) I, II and III
C) II, III and IV
D) I, II, III, IV and V
24. Which intermediate filament protein is correctly matched with its corresponding tissue type?
I – Neurofilament – Neurons
II – Desmin – Muscle cells
III – Keratin – Epithelial cells
IV – Vimentin – Mesenchymal cells
A) I Only
B) I and II
C) I, II and III
D) I, II, III and IV
25. Assertion (A): The KDEL receptor binds cargo in the Golgi and releases it in the ER.
Reason (R): The receptor has high affinity at the acidic pH of the Golgi and low affinity at the neutral pH of the ER.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is not the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.
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References
- Cooper, G. M. (2022). The Cell: A Molecular Approach, Sinauer Associates, 9th Edition
- Willey, J. M., Sandman, K. M., & Wood, D. H. (2022). Prescott’s Microbiology, McGraw-Hill, 12th Edition
- Kumar, P., & Mina, U. (2025). Life Sciences: Fundamentals and Practice – Part I & II, Pathfinder Academy, 9th Edition
- Verma, P. S., & Agarwal, V. K. (2022). Cell Biology, Genetics, Molecular Biology, Evolution and Ecology, S. Chand Publishing, 1st Edition
- Singh, B. D. (2020). Genetics, Kalyani Publishers
- Nelson, David L. & Cox, Michael M. (2021). Lehninger Principles of Biochemistry, W. H. Freeman, 8th Edition
