CSIR UGC NET Life Sciences Mock Test 2026: Interactive Unit 2 Practice Paper
Boost Your CSIR NET JRF Rank with High-Yield Cell Biology Questions | Fully Explained Interactive Practice Set
Are you looking to crack the CSIR UGC NET Life Sciences exam with a top rank? Mastering Unit 2: Cellular Organization (Cell Biology) is one of the most reliable strategies to guarantee maximum scores in both Part B and Part C. To assist your preparation, our expert panel has designed this exclusive, interactive full-length unit-specific mock test strictly matching the latest examination standards.
Exam Pattern Followed: This test contains exactly 50 questions broken down into Part A (General Aptitude), Part B (Core Cell Biology), and Part C (Analytical Cell Biology) with instant feedback & comprehensive explanations upon selecting your choice!
📋 Mock Test Scheme & Guidelines
- Total Questions: 50 (Part A: 10 Questions | Part B: 25 Questions | Part C: 15 Questions)
- Marking System: Part A (+2 | -0.5), Part B (+2 | -0.5), Part C (+5 | -1.0)
- Syllabus Scope: General Aptitude & Unit 2 (Cellular Organization)
PART A: General Aptitude & General Science
(2 Marks each. Negative marking: 0.5)
Q1. If 4 men or 6 women can build a wall in 20 days, how long will it take 6 men and 3 women to build the same wall working together at the same pace?
Explanation: 4 men = 6 women ⇒ 1 man = 1.5 women. Thus, 6 men + 3 women = 6(1.5) + 3 = 12 women. Since 6 women take 20 days, 12 women will take (6 × 20) / 12 = 10 days.
Q2. A group of cells doubles in count every 30 minutes. If a single petri dish is completely full of these cells at exactly 4:00 PM, at what time was the petri dish exactly 25% full?
Explanation: If the dish is 100% full at 4:00 PM, it was 50% full 30 minutes earlier (3:30 PM), and 25% full another 30 minutes earlier, which is 3:00 PM.
Q3. Find the missing number in the following mathematical series: 2, 6, 12, 20, 30, ?, 56.
Explanation: The difference between consecutive terms increases by 2 each time (+4, +6, +8, +10, +12...). So, 30 + 12 = 42. Next is 42 + 14 = 56.
Q4. In a cross-country sprint race, if runner A is faster than B, runner B runs at the same pace as C, and runner D is slower than C, who among them is definitely the slowest runner?
Explanation: The speed relationships are: A > B, B = C, and C > D. Combining these gives us A > B = C > D, identifying D unambiguously as the slowest.
Q5. What is the angle between the hour hand and the minute hand of a standard clock at exactly 3:40?
Explanation: Using the formula: Angle = |(30H - 5.5M)|, where H = 3 and M = 40. Angle = |30(3) - 5.5(40)| = |90 - 220| = 130 degrees.
Q6. The average weight of 5 distinct protein samples is 45 kDa. When a 6th protein sample is added to the batch, the new mean weight drops to 43 kDa. What is the molecular weight of the 6th protein?
Explanation: Total weight of 5 samples = 5 × 45 = 225 kDa. Total weight of 6 samples = 6 × 43 = 258 kDa. Weight of the 6th sample = 258 - 225 = 33 kDa.
Q7. A bag contains 4 red labels, 5 blue labels, and 6 green labels. If two labels are drawn randomly from the bag one after another without replacement, what is the probability that both labels are blue?
Explanation: Probability of first blue label = 5/15 = 1/3. Probability of second blue label = 4/14 = 2/7. Combined probability = (1/3) × (2/7) = 2/21.
Q8. In a certain scientific code language, 'RIBOSOME' is written as 'VMFPTOSJ'. How would 'NUCLEOPH' be written in that exact same code variant?
Explanation: The letters are shifted forward according to specific pattern variations. For NUCLEOPH, matching the same reverse-position alphanumeric increment yields RVFMIPQS.
Q9. A rectangular laboratory storage zone measures 12 meters in length, 9 meters in width, and 8 meters in height. What is the length of the longest structural diagnostic rod that can be fit completely inside this room corner-to-corner?
Explanation: Longest diagonal of a cuboid = √(l² + w² + h²) = √(12² + 9² + 8²) = √(144 + 81 + 64) = √289 = 17 meters.
Q10. A student walks 6 km North, takes a precise left turn and walks 8 km, then takes a final left turn and walks 6 km. How far and in which direction is the student from the original starting point?
Explanation: Moving North 6 km and then South 6 km cancels out the vertical displacement. The horizontal displacement remains exactly 8 km to the West.
PART B: Subject Core (Unit 2 - Cellular Organization)
(2 Marks each. Negative marking: 0.5)
Q11. Which of the following lipid types is explicitly restricted to the outer (exoplasmic) leaflet of the plasma membrane in healthy, non-apoptotic mammalian cells?
Explanation: Gangliosides and other glycolipids are synthesized in the lumen of the Golgi apparatus and are exclusively displayed on the exoplasmic leaflet. Phosphatidylserine is flipped to the outside only during apoptosis.
Q12. During FRAP (Fluorescence Recovery After Photobleaching) kinetics analysis, which parameter measures the overall percentage of membrane protein molecules capable of free lateral diffusion?
Explanation: The mobile fraction quantifies the extent of fluorescence recovery at the plateau phase relative to initial levels, defining the proportion of molecules free to diffuse.
Q13. Which transport protein catalyzes the active ATP-driven trans-bilayer movement of aminophospholipids from the exoplasmic leaflet to the cytosolic leaflet?
Explanation: Flippases use ATP to transport lipids inwardly (outer to inner leaflet), while floppases move them outward, and scramblases move them bidirectionally independent of ATP.
Q14. Gram-negative bacteria contain a distinct structural layer between their inner plasma membrane and outer membrane known as:
Explanation: Gram-negative bacteria possess a periplasmic space containing a thin peptidoglycan layer, bounded by the inner and outer membranes.
Q15. What is the core biochemical composition of the bacterial cell wall principal network?
Explanation: The bacterial cell wall peptidoglycan (murein) consists of alternating NAG and NAM residues linked by beta-1,4-glycosidic bonds and crosslinked by amino acid side chains.
Q16. The nuclear localization signal (NLS) required for the importing of proteins into the nucleus is primarily enriched in which amino acids?
Explanation: Classical NLS sequences (like that of SV40 T-antigen) are rich in basic, positively charged amino acids like lysine and arginine.
Q17. Which GTPase is directly responsible for powering the nucleocytoplasmic cargo transport cycle through its differential compartmental concentration gradient?
Explanation: Ran GTPase establishes a gradient (RanGTP high in nucleus, RanGDP high in cytoplasm) that controls cargo binding and release by importins and exportins.
Q18. Core N-linked glycosylation of nascent polypeptide chains initiates inside which organelle or compartment?
Explanation: N-linked glycosylation begins co-translationally in the ER lumen, where a pre-assembled 14-sugar oligosaccharide is transferred to an asparagine residue.
Q19. Proteins destined for degradation via the lysosomal pathway are tagged or modified in the Golgi apparatus with which specific chemical moiety?
Explanation: Soluble lysosomal enzymes are specifically modified with mannose-6-phosphate residues in the cis-Golgi to be recognized by M6P receptors in the TGN for sorting to lysosomes.
Q20. Which specific coat protein complex is responsible for mediating retrograde transport from the Golgi apparatus back to the Endoplasmic Reticulum?
Explanation: COPI vesicles mediate retrograde transport (Golgi to ER), while COPII coats anterograde transport vesicles (ER to Golgi).
Q21. During cellular respiration, protons are actively pumped out of the mitochondrial matrix into which specific compartment to establish the proton motive force?
Explanation: Complexes I, III, and IV pump protons from the matrix into the intermembrane space, creating the electrochemical gradient utilized by ATP synthase.
Q22. Plant vacuoles maintain an internal acidic pH primarily through the action of which specific ion pumps?
Explanation: Vacuolar membranes (tonoplasts) feature active V-type ATPases and proton-pumping pyrophosphatases that move H+ into the vacuole against its gradient.
Q23. Which cytoskeletal filament system lacks intrinsic structural polarity and does not utilize motor proteins for direction-specific cargo translocation?
Explanation: Intermediate filaments are symmetric, non-polar polymers assembled from staggered tetramers, unlike polar microtubules or actin tracks.
Q24. Which motor protein complex moves progressively along microtubule tracks exclusively toward the minus (-) end (retrograde transport)?
Explanation: Cytoplasmic dyneins are minus-end directed microtubule motors, while most kinesins migrate toward the plus end.
Q25. The critical concentration (Cc) threshold for actin filament assembly is lowest at which structural end?
Explanation: The barbed (+) end has a much lower critical concentration (Cc ~ 0.1 µM) than the pointed (-) end (Cc ~ 0.6 µM), allowing preferential growth at the plus end.
Q26. Which chromosome architecture element keeps sister chromatids securely paired along their length until the onset of anaphase?
Explanation: Cohesin ring complexes hold sister chromatids together from S-phase until they are proteolytically cleaved by separase at the metaphase-anaphase transition.
Q27. Activation of the maturation promoting factor (MPF / Cyclin B-Cdk1 complex) requires the specific enzymatic removal of inhibitory phosphates by which phosphatase?
Explanation: Wee1 kinase places inhibitory phosphates on Thr14 and Tyr15 of Cdk1. Cdc25 phosphatase removes these inhibitory phosphates to activate MPF.
Q28. The Spindle Assembly Checkpoint (SAC) prevents premature sister chromatid separation by directly inhibiting which enzymatic target?
Explanation: Unattached kinetochores generate a wait signal via Mad2/Bub3 that inhibits APC/C-Cdc20, preventing securin degradation.
Q29. Which cell cycle phase contains the crucial restriction point (R-point) beyond which cellular replication proceeds independent of external mitogenic growth signals?
Explanation: The restriction point occurs in late G1. Once cells pass this point, they are committed to complete S phase and division even if growth factors are removed.
Q30. Peroxisomes are distinct metabolic organelles containing high levels of which enzyme to neutralize reactive hydrogen peroxide molecules?
Explanation: Peroxisomes use oxidases to break down fatty acids, generating H2O2. Catalase converts toxic H2O2 into safe water and oxygen.
Q31. What type of heterochromatin remains permanently condensed and transcriptionally inactive across all developmental stages in all cell variants of an organism?
Explanation: Constitutive heterochromatin (e.g., centromeres, telomeres) is permanently inactive, whereas facultative heterochromatin can be conditionally activated in specific cell lineages.
Q32. Polytene chromosomes, frequently analyzed in Drosophila larval salivary glands, form via which altered replication pathway?
Explanation: Endoreplication involves repeated rounds of DNA synthesis without intervening cell division or chromatid separation, forming massive multi-stranded giant polytene structures.
Q33. Translocation of proteins into the matrix of mitochondria occurs primarily through the coordinated action of which outer and inner membrane translocon complexes?
Explanation: Proteins are threaded through the Translocase of Outer Membrane (TOM) and Translocase of Inner Membrane (TIM) to enter the mitochondrial matrix.
Q34. Which basic protein component forms the structural octameric core around which eukaryotic genomic DNA wraps to yield a nucleosome bead?
Explanation: The nucleosome core consists of two copies each of histones H2A, H2B, H3, and H4. Histone H1 acts as the linker histone outside the core.
Q35. The degradation of targeted misfolded proteins within the eukaryotic cytoplasm is carried out by which complex machinery?
Explanation: Cytoplasmic polyubiquitinated proteins are recognized, unfolded, and degraded inside the cylindrical 26S proteasome chamber.
PART C: Subject Analytical (Unit 2 Higher-Order Problems)
(5 Marks each. Negative marking: 1.0)
Q36. Researchers isolate a mutant mammalian cell line displaying a defective SRP (Signal Recognition Particle) receptor that can bind SRP but fails to interact effectively with the Sec61 translocon. Which cellular phenotype would you expect to observe in this mutant line?
Explanation: The SRP receptor hands off the signal sequence/ribosome complex to the translocon. If this hand-off fails, co-translational translocation into the ER lumen cannot proceed, causing targeted proteins to be synthesized or released into the cytosol.
Q37. You are measuring the phase transition profile of artificial lipid vesicles. If you significantly increase the relative concentration of long-chain saturated fatty acids while decreasing cholesterol concentrations at high environmental temperatures, what will be the collective effect on membrane transition temperature (Tm) and fluidity?
Explanation: Long-chain saturated fatty acids pack tightly together due to straight acyl tails, increasing hydrophobic interactions. This raises the transition temperature (Tm) required to melt the membrane, thereby decreasing fluidity.
Q38. A conditional yeast mutant exhibits a defective Sar1 GEF (Sec12). When shifting this strain to a non-permissive restrictive temperature, what cellular consequence will occur within the secretory pathway?
Explanation: Sec12 is the GEF that exchanges GDP for GTP on Sar1. Active Sar1-GTP exposes an amphipathic helix to insert into the ER membrane, recruiting Sec23/24 to begin COPII vesicle formation. Without it, ER export stops completely.
Q39. To determine if a protein behaves as an integral membrane component or a peripheral membrane protein, scientists treat isolated cellular fractions with a high-salt buffer containing 1M NaCl. What result diagnoses the protein as a peripheral membrane protein?
Explanation: Peripheral membrane proteins associate with the membrane surface via electrostatic interactions and hydrogen bonds, which are easily disrupted by high ionic strength (high salt), releasing them into solution. Integral proteins require detergents to solubilize.
Q40. During an in vitro cell-free translation experiment, a secretory protein containing an amino-terminal ER signal sequence is translated using pure ribosomes and amino acids. If microsomes are added to the tube only AFTER translation has fully concluded, what will be the fate and state of the protein?
Explanation: In mammals, translocation into the ER is strictly co-translational. Once translation finishes, the protein folds into a conformation that cannot pass through the narrow translocon pore, meaning it stays outside the microsomes.
Q41. You introduce a non-hydrolyzable structural analogue of GTP (GTP-gamma-S) into a cell-free assembly system containing purified tubulin heterodimers. What specific feature of microtubule dynamics will you observe in this mix?
Explanation: Hydrolysis of GTP to GDP is what destabilizes the microtubule lattice and triggers catastrophe. If tubulin incorporates non-hydrolyzable GTP-gamma-S, the stable GTP cap is never lost, allowing continuous growth without disassembly.
Q42. A line of human fibroblasts contains a mutant variant of the Rb (Retinoblastoma) protein that cannot be phosphorylated by G1-Cdk or G1/S-Cdk complexes. What will be the cell cycle proliferation status of these mutant cells?
Explanation: Unphosphorylated Rb binds and inhibits the E2F transcription factor. Cdk phosphorylation normalerweise releases Rb from E2F to turn on S-phase genes. If Rb cannot be phosphorylated, it permanently represses E2F, causing G1 arrest.
Q43. Cytochalasin D is a drug that binds specifically to the (+) barbed ends of actin microfilaments and prevents subunit addition. If you add Cytochalasin D to a system undergoing active actin filament treadmilling, what structural change will take place over time?
Explanation: Treadmilling relies on subunit addition at the plus end and loss at the minus end. Blocking the plus end with Cytochalasin D while disassembly continues at the minus end causes the filaments to shorten and shrink away.
Q44. A patient presents with a rare genetic disorder characterized by severe muscle weakness and abnormal intracellular accumulation of long-chain fatty acids. Structural analysis reveals a defect in importing matrix enzymes containing a carboxy-terminal SKL signal sequence. Which organelle is malfunctioning in this patient?
Explanation: The C-terminal tripeptide Ser-Lys-Leu (SKL) is the classic Peroxisomal Targeting Signal 1 (PTS1), recognized by Pex5 import factors. Defects here cause peroxisomal import failures like those seen in Zellweger spectrum disorders.
Q45. During an experimental assay, you microinject a large dose of constitutively active Ran-GEF (RCC1) directly into the cytoplasmic compartment of a eukaryotic cell. How will this manipulation alter nuclear transport mechanics?
Explanation: RanGTP promotes cargo release from importin. Ran-GEF converts RanGDP to RanGTP. Normally, Ran-GEF is restricted to the nucleus so that release only happens there. Flooding the cytoplasm with RanGTP causes importins to drop their cargo before ever reaching the nucleus.
Q46. Digitonin permeabilizes plasma membranes by extracting cholesterol molecules but leaves inner organelle systems largely intact. If you treat cells with digitonin alongside a cytoplasmic protease, which protein pool will remain completely protected from digestion?
Explanation: Digitonin punctures the outer plasma membrane but spares organelle membranes, keeping lumenal ER and Golgi enzymes sequestered away from the introduced cytosolic protease.
Q47. Cell fusion experiments bring together a mammalian cell in G1 phase with another cell in M phase. What immediate structural transition happens within the G1 nucleus after cytoplasmic fusion?
Explanation: Active MPF (Cyclin B-Cdk1) from the M-phase cell diffuses throughout the shared cytoplasm, driving the G1 chromatin to condense prematurely into single-chromatid threads.
Q48. You treat dividing animal cells with Taxol (Paclitaxel), a drug that binds and stabilizes microtubule polymers against depolymerization. At which precise phase of the mitotic cycle will these cells arrest?
Explanation: Taxol prevents spindle microtubule dynamics, preventing proper chromosome alignment and tension sensing at the kinetochores. This leaves the Spindle Assembly Checkpoint (SAC) permanently active, blocking anaphase entry.
Q49. If a eukaryotic gene encodes a protein containing an amino-terminal ER signal sequence, an internal nuclear localization signal (NLS), and a carboxy-terminal KDEL retrieval sequence, what will be the final steady-state destination of this protein?
Explanation: The N-terminal ER signal sequence acts co-translationally, routing the ribosome-peptide complex to the ER before the downstream NLS is ever translated or exposed to the cytosol. Once inside the ER lumen, the C-terminal KDEL tag ensures its retention there via retrograde retrieval pathways.
Q50. A unique line of mutant yeast cells lacks functional Sec17 and Sec18 proteins (homologues of mammalian alpha-SNAP and NSF). Which step of vesicle trafficking will be blocked in these cells?
Explanation: NSF (Sec18) and alpha-SNAP (Sec17) use the energy of ATP hydrolysis to untangle and separate tightly bundled cis-SNARE complexes after a fusion event, allowing the individual SNARE proteins to be recycled for future transport rounds.
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