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6.1 The Nucleus — Test 1
Q1. The nucleus was first discovered in 1831 by:✓ Robert Brown
Q2. The major structural protein underlying the nuclear envelope is:✓ Lamin
Q3. One of the following is NOT a cytoplasmic organelle of the cell:✓ Nucleolus
Q4. The basic structural unit of DNA packaging in eukaryotes is known as:✓ The nucleosome
Q5. The filamentous DNA-and-protein complex that can be stained in interphase nuclei is called:✓ Chromatin
Q6. Euchromatin is characterized by:✓ Active gene transcription
Q7. The core of the nucleosome is made up of which histones?✓ H2A, H2B, H3, H4
Q8. In eukaryotic cells, the assembly of ribosomal subunits takes place in the:✓ Nucleoli
Q9. The chief metallic ion involved in the assembly of ribosomal subunits is:✓ Mg²⁺
Q10. Which statement is correct for the nucleolus?✓ Clustering of ribosomal-RNA genes and their transcription
Q11. Which one of the following statements about the nucleolus is FALSE?✓ It is surrounded by a lipid-bilayer membrane
Q12. The presence of the nucleolus within the nucleus can be differentially located using:✓ Pyronine–methyl green stain
Q13. The number of nuclear pores depends on the:✓ Transcription activity of the cell
Q14. Movement of proteins larger than ~50 kDa across the nuclear envelope requires:✓ Importin β
Q15. The nuclear localization signal (NLS) almost always comprises which amino acids?✓ Lysine and arginine
Q16. In the context of protein import into the nucleus, which molecule releases the cargo from the import receptor?✓ Ran
Q17. The presence of a nuclear localization signal (NLS) in a steroid receptor indicates that, before ligand binding, the receptor resides:✓ In the cytosol
Q18. All cytosolic proteins bearing nuclear export signals are removed from the nucleus when it reassembles after:✓ Mitosis
Q19. The nuclear matrix is best described as:✓ A complex network of protein and RNA fibrils that make up the nuclear substructure
Q20. Lampbrush chromosomes are found in the:✓ Amphibian oocytes
Q21. Lampbrush chromosomes are seen at which stage of meiosis?✓ Diplotene of prophase I
Q22. Chromosomes carrying a nucleolar organizer region (NOR) are also called satellite chromosomes because:✓ The decondensed NOR makes the adjacent segment appear separated
Q23. If a piece of chromatin contained 200 copies of histone H4, how many nucleosomes would it contain?✓ 100
Q24. The canonical signature motif for EXPORT of proteins from the nucleus (nuclear export signal) is:✓ -Leu-Ala-Leu-Lys-Leu-Ala-Gly-Leu-Asp-Ile
Q25. Which sequence is typically used to IMPORT proteins into the nucleus?✓ -Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val-
6.1 Chromatin & Chromosome Organization — Test 2
Q26. A scientist characterizes chromatin from a novel organism. Which feature would be NOVEL relative to most eukaryotes?✓ A nucleosome core octamer comprising pairs of histones H1, H2, H3A and H3B
Q27. What is observed if histones are depleted from a metaphase chromosome and viewed under a transmission electron microscope?✓ A protein scaffold with a huge number of DNA loops
Q28. Which compartment in the human nucleus is associated with gene silencing?✓ The perinuclear domain (nuclear periphery)
Q29. Which statement about human chromosomes is TRUE?✓ Gene-dense chromosomes tend to localise toward the centre of the nucleus
Q30. Which statement holds true for the G0/G1 organization of chromosomal DNA in a mature eukaryotic nucleus?✓ Organized in constrained locations; interacts with other chromosomal DNA non-randomly
Q31. Proteins use a nuclear localization signal (NLS) for import. Consider these statements:✓ A and B
Q32. The Ran GTPase imposes directionality on nuclear transport. Which combination contains all the CORRECT statements?✓ A, B, D, E
Q33. Nuclear import of cytoplasmic proteins through the nuclear pore complex requires:✓ A, B and D
Q34. Cells were transfected with a vector encoding either β-galactosidase (β-gal) alone or a β-gal–glucocorticoid receptor (GR) fusion, then kept with or without dexamethasone; β-gal was localized by immunofluorescence. Consider:✓ 1, 2 and 4
Q35. Chromatin condensation is driven by condensins (SMC proteins). If cells are treated with an inhibitor of Cdk1 phosphorylation immediately before they enter M phase, which statement is most likely TRUE?✓ Sister chromatids are held together by cohesins along the entire chromosome
6.2 Endoplasmic Reticulum — Test 3
Q36. Ribophorins are a group of:✓ Transmembrane glycoproteins located in the membrane of the RER
Q37. The cell organelle in which detoxification of xenobiotics takes place is the:✓ SER
Q38. Drug detoxification in the smooth endoplasmic reticulum is carried out by specialized enzymes called:✓ Mixed-function oxidases (monooxygenases)
Q39. The smooth endoplasmic reticulum is involved in the synthesis of which of the following?✓ Both B and C
Q40. Which organelle is involved in the de novo synthesis of membrane?✓ Endoplasmic reticulum
Q41. Which amino acid in a polypeptide undergoes N-linked glycosylation in the lumen of the rough ER?✓ Asparagine
Q42. Which one of the following is NOT a function of the rough endoplasmic reticulum?✓ O-linked glycosylation of proteins
Q43. The prerequisite for the entry of secretory, lysosomal and plasma-membrane proteins into the endoplasmic reticulum is:✓ Presence of a signal sequence
Q44. Membrane-bound and free ribosomes are structurally identical but, at a given time, differ in their association with:✓ Nascent proteins (their signal sequences)
Q45. Why is a hydropathy plot employed?✓ To investigate the transmembrane domains of proteins
Q46. A C-terminal sequence of four amino acids, Lys-Asp-Glu-Leu (KDEL), directs a protein to which organelle?✓ Endoplasmic reticulum
Q47. Molecular chaperones facilitate:✓ Proper folding of newly synthesized proteins
Q48. Which of the following is NOT a chaperone?✓ HSF1
Q49. Which heat-shock protein is present in almost every compartment of the eukaryotic cell?✓ Hsp70
Q50. Which one of the following is NOT a feature of chaperones?✓ Ubiquilin is one of the most important chaperones
Q51. Which one of the following activities is NOT involved in protein folding in the endoplasmic reticulum?✓ Protein ubiquitination
Q52. Pulse-chase labelling is used to determine:✓ The fate (trafficking) of a synthesized protein
Q53. Which of the following statements are TRUE for the endoplasmic reticulum?✓ a, b and c
Q54. During protein transport across the endoplasmic reticulum, the role of SRP is to:✓ Associate with the signal peptide, pause translation, bind the SRP receptor, and promote co-translational transport of the polypeptide
Q55. Choose the INCORRECT statement about the signal recognition particle (SRP):✓ It contains a signal-peptidase activity
Q56. Ribosomes attach to the endoplasmic reticulum via:✓ The translated nascent chain, which carries a signal that interacts with the SRP receptor on the ER
Q57. Multi-pass (membrane-spanning, multiple-helix) plasma-membrane proteins are characterized by:✓ Co-translational capture of an internal targeting sequence and stop-transfer sequences in the ER
Q58. Which of the following statements about membrane-spanning proteins are TRUE?✓ A, B and C
Q59. Which proteins are translated on the rough endoplasmic reticulum?✓ Proteins targeted to lysosomes, the plasma membrane and the cell exterior
Q60. The tetrapeptide KDEL is a retrieval signal. From this, the receptor for KDEL is mainly localized in the:✓ Golgi (cycling between Golgi and ER)
Q61. An mRNA for a secretory protein translated in a rabbit reticulocyte lysate gives a 400 kDa product, but with added dog-pancreas microsomes gives a 360 kDa product. The 40 kDa difference is due to:✓ Loss of a 40 kDa peptide from the N-terminus
Q62. Consider the KDEL receptor:✓ A, C and D
Q63. A scientist mutates an ER-resident protein-folding enzyme (PFE) so it loses its KDEL retention sequence. The most probable consequences are:✓ 1 and 3 only
Q64. A secreted glycoprotein X (with NO N-linked glycosylation site) is tagged with a C-terminal KDEL and expressed from an inducible promoter. At 20 and 60 min, purified ER shows higher-molecular-weight bands of X-KDEL. The most likely explanation is that the protein was:✓ Modified in the Golgi prior to being retrieved back to the ER
Q65. Membrane proteins are sorted partly by hydrophobic matching (shorter transmembrane segments partition into thinner membranes). Given that Golgi transmembrane segments are shorter than plasma-membrane ones, that cholesterol increases bilayer thickness, and that Golgi and plasma membranes share the same phospholipids, it follows that:✓ Proteins in the plasma membrane have longer transmembrane portions than those in the Golgi
Q66. Which of the following statements about the Hsp90 chaperone system are correct?✓ II and IV
Q67. Which lectin functions in the ER-associated degradation (ERAD) pathway by recognising misfolded glycoproteins?✓ OS-9
Q68. If the amino-acid side-chains of a properly folded protein fail to get appropriately modified in the ER–Golgi, the protein will be:✓ Degraded through the ER-associated degradation (ERAD) pathway
6.3 Golgi Apparatus — Test 4
Q69. Glycosyltransferases and glycosidases are predominantly found in which cell organelle?✓ Golgi apparatus
Q70. The primary function of the Golgi apparatus in eukaryotic cells is:✓ Modification and packing of proteins
Q71. The major biochemical role of the Golgi apparatus is:✓ Glycosylation of lipids and proteins
Q72. If the Golgi apparatus is associated with secretion, we would expect it most abundantly in:✓ Gland
Q73. The acrosome of a spermatozoan is derived from the:✓ Golgi complex
Q74. Glycosylation of proteins happens in the:✓ Endoplasmic reticulum and Golgi
Q75. Modification of proteins as they pass through the Golgi includes all of the following EXCEPT:✓ Signal-sequence removal
Q76. Addition of N-linked oligosaccharides is done:✓ In the ER and then modified in the Golgi
Q77. Abundant Golgi vesicles near the cell plate during late telophase/cytokinesis of a plant cell reflect the Golgi's role in:✓ Polysaccharide synthesis
Q78. In animal cells the Golgi sits close to the nucleus. Which component is directly involved in this correct Golgi localization?✓ Microtubules
Q79. The Golgi is called the 'cellular post office'. Monensin inhibits trafficking through the Golgi. After monensin treatment, the Golgi will appear:✓ Swollen
Q80. Choose the correct combination of statements about the Golgi complex:✓ 2, 3 and 5 only
Q81. Glycolipids and sphingomyelin are made by adding sugars or phosphorylcholine to ceramide on the cytosolic and luminal Golgi surfaces; the finished molecules end up on the outer leaflet of the plasma membrane. What events achieve this localization?✓ Action of a flippase and membrane fusion
Q82. A GFP-tagged protein localizes to the Golgi (pericentrosomal). A new drug disrupts the Golgi into small vesicles. Which are plausible targets of the drug?✓ A and C only
6.4 Protein Trafficking & Secretion — Test 5
Q83. Membranes of which one of the following pairs are contiguous (physically continuous)?✓ Nucleus and ER
Q84. The endomembrane system of a cell includes:✓ Lysosomes, Golgi complex and endoplasmic reticulum
Q85. The mitochondrion is NOT considered part of the endomembrane system because it:✓ Is not derived from the ER or Golgi
Q86. The correct order of the secretory pathway for proteins in a mammalian cell is:✓ Rough ER → Golgi transport vesicle → Golgi → secretory vesicle → cell surface
Q87. Which membrane-associated process involves the formation of clathrin-coated vesicles?✓ Receptor-mediated endocytosis
Q88. The protein involved in receptor-mediated endocytosis is:✓ Clathrin
Q89. Vesicles transporting proteins from the plasma membrane to endosomes are coated by:✓ Clathrin
Q90. Proteins bearing mannose-6-phosphate and a C-terminal KDEL sequence are directed, respectively, into the:✓ Lysosome and endoplasmic reticulum
Q91. Translocation into which one of the following organelles does NOT depend on an amino-acid sequence as the import signal?✓ Lysosome
Q92. Which of the following is NOT an example of transmembrane transport between subcellular compartments?✓ Transport from the ER to the Golgi complex
Q93. A protein synthesized on cytosolic (free) ribosomes, traced by pulse-chase, is most likely found in the:✓ Nucleus
Q94. A fluorescently tagged secretory protein in yeast is observed in: A. the Golgi, B. secretory vesicles, C. the rough ER. Which is the correct temporal sequence of these events?✓ C → A → B
Q95. In an in-vitro transport assay, which combination of organelles is competent to import isolated (already-made) proteins post-translationally?✓ Peroxisomes and nucleus
Q96. Consider these statements about protein trafficking:✓ A, B and D
Q97. Which statements regarding trafficking motors/scaffolds are CORRECT?✓ A and C
Q98. Match each organelle (List I) with the signal that targets proteins to it (List II):✓ A-iv, B-iii, C-i, D-ii
Q99. A mutant Arf protein is constitutively GTP-bound but defective in GTP hydrolysis. Regarding vesicle formation, transport and fusion:✓ B and C only
Q100. Protein 'A' tagged with GFP (A-GFP) co-localizes with LAMP1. In the presence of bafilomycin A (a V-type H⁺-ATPase inhibitor), A-GFP no longer co-localizes with LAMP1 but instead co-localizes with LC3 puncta. Which statement is TRUE?✓ Autophagy is required for trafficking of A-GFP to lysosomes
6.5 Lysosomes & Endosomal System — Test 6
Q101. Acidic organelles that contain a battery of degradative enzymes are:✓ Lysosomes
Q102. Which cell organelle is called the 'suicidal bag'?✓ Lysosome
Q103. The polymorphous organelle of a eukaryotic cell is the:✓ Lysosome
Q104. The organelle considered the best indicator of cellular injury is the:✓ Lysosomes
Q105. Which enzyme is used as a marker for the lysosomal fraction?✓ Acid phosphatase
Q106. Cathepsin enzymes produced by lysosomes act on:✓ Protein
Q107. Which of the following enzymes is NOT found in lysosomes?✓ Acetylcholine esterase
Q108. Which of the following enzymes is NOT found in lysosomes?✓ Resolvase
Q109. The very low internal pH of lysosomes is achieved by:✓ Proton pumps that move protons against the concentration gradient
Q110. The cell maintains a high concentration of protons inside the lysosome because of:✓ An ATP-powered proton pump in the lysosomal membrane
Q111. The sugar moiety important for targeting acid hydrolases from the Golgi to lysosomes is:✓ Mannose-6-phosphate
Q112. The mannose-6-phosphate-dependent pathway for routing lysosomal enzymes can be blocked by:✓ Tunicamycin
Q113. Early and late endosomes are developmental stages associated with which organelle?✓ Lysosomes
Q114. Which one of the following is a marker for early endosomes?✓ Rab5
Q115. Autophagy is facilitated by:✓ Lysosomes
Q116. The process that supplies intracellular macromolecules for lysosomal degradation during nutrient starvation is:✓ Autophagy
Q117. An autophagosome is:✓ A double-membraned vesicle characteristic of macroautophagy
Q118. Degradation of excess secretory vesicles in endocrine glands, by their fusion with lysosomes, is called:✓ Crinophagy
Q119. Which of the following diseases is NOT linked to lysosomes?✓ Marfan syndrome
Q120. Metachromatic leukodystrophy (MLD), caused by deficiency of arylsulfatase A and affecting the CNS, is:✓ A lysosomal storage disorder
Q121. In Tay-Sachs disease, glycolipids (gangliosides) accumulate, especially in nerve cells. This is due to a specific defect in:✓ A lysosomal enzyme that catalyses a step in ganglioside breakdown
Q122. What happens if a lysosome leaks (ruptures) inside a living cell?✓ Acid hydrolases come out and digest cellular components
Q123. The following statements relate to lysosomes. Choose the combination with all correct answers.✓ I, III and IV only
Q124. Consider these statements about autophagy:✓ D and A
Q125. A null mutation is created in the gene responsible for phosphorylating mannose at the 6th carbon on acid hydrolases in the cis-Golgi. Which statements explain the outcome?✓ A and B
6.6 Peroxisomes — Test 7
Q126. Which intracellular organelle contains copious amounts of the enzyme catalase?✓ Peroxisome
Q127. Peroxisomes are surrounded by:✓ A single membrane
Q128. Which one of the following organelles is enclosed by a single membrane?✓ Endoplasmic reticulum
Q129. Which of the following has NO DNA?✓ Golgi apparatus
Q130. Which peroxisomal enzyme is active in breaking down fatty acids?✓ Acetyl-CoA oxidase
Q131. Which of the following enzymes are found in peroxisomes?✓ A, B and C
Q132. Which one of the following statements is NOT true?✓ Fatty-acid biosynthesis occurs in peroxisomes
Q133. Which of the following are correct statements about peroxisomal protein import?✓ A, B and C