Cell biology & Molecular Biology | CSIR NET Life Science | CSIR NET Final Sprint 2025 | PW

TLDR;

This YouTube video features a session focused on cell biology and molecular biology questions designed to help students prepare for the IIT JAM and CSIR NET exams. Instructors provide mock questions, detailed explanations, and revision tips, emphasizing the importance of understanding core concepts and applying them to problem-solving. The session includes interactive problem-solving, concept revision, and test-taking strategies.

Mock Questions for IIT JAM and CSIR NET
Detailed Explanations and Revision Tips
Interactive Problem-Solving and Concept Revision

Introduction [0:25]

The session is designed to provide new types of questions in cell biology and molecular biology to boost exam preparation. The series will continue with challenging questions to encourage active learning and revision. Students are advised to take notes and identify topics needing further review. The instructors highlight the benefit of having two sessions, allowing for immediate revision of topics covered in the first session before the next one.

Question 1: Protein Localization and SRP [3:04]

The first question focuses on protein localization, specifically the roles of signal peptides and Signal Recognition Particle (SRP) in directing proteins to the endoplasmic reticulum (ER). The signal peptide guides proteins to the ER, and SRP recognizes this peptide. A mutation in SRP that disrupts its binding to the signal peptide will most strongly affect ER-targeted proteins. Cytosolic metabolic enzymes do not go to the ER, nuclear transcription factors require a nuclear localization signal (NLS), secreted growth factors pass through the ER and Golgi, and mitochondrial matrix proteins use a post-translational pathway.

Question 2: Exon Skipping and Splicing [8:54]

This question discusses a situation where exon skipping in a Catenin isoform results in the deletion of a calcium-binding repeat. This is most likely due to a mutation in an exonic splicing enhancer, which typically binds SR proteins involved in spliceosome-mediated splicing. Mutations in the promoter would affect mRNA production, and RNA editing occurs after mRNA formation, making these options less relevant to exon skipping.

Question 3: Positive Feedback Loop and Lac Operon [12:36]

The question describes a positive feedback loop where a receptor increases its own expression by recruiting transcription factors. The graph that reflects lac operon-like behavior is a sigmoidal shape curve, representing cooperative increase. The question uses the hint of "Lac Operon like behavior" to point to the correct answer.

Question 4: Protein Mis-folding and ERAD [17:21]

A misfolded protein retained by BiP in the ER undergoes ER-associated degradation (ERAD) involving ubiquitination. The protein will not proceed to the Golgi, be secreted, or reach the nucleus. Vesicle budding is also not an option since the protein is being retained for degradation.

Question 5: Matching Molecular Biology Processes [18:38]

This question requires matching molecular biology components with their processes. The correct matches are: Sigma factor with transcription, aminoacyl-tRNA synthetase with activation of amino acids and attachment to tRNA, and primase with DNA replication. The incorrect match is Rho factor with translation, as Rho factor is involved in transcription termination in prokaryotes.

Question 6: Cell Membrane Features [20:38]

The question asks which features about cell membranes are correct. The correct statements are that cell membranes are made of membrane lipids and proteins, define boundaries between cytosol organelles and the extracellular environment, and regulate the movement of charged molecules. The incorrect statements are that they transport hydrophobic molecules between compartments (without specifying size) and allow the passive diffusion of ions across the lipid bilayer.

Question 7: Replicative Transposons [25:35]

The question focuses on replicative transposons, which generate a copy of themselves to insert at a new location while the original sequence remains in place. This contrasts with other mechanisms involving excision or non-replicative transposition.

Question 8: Calcium-Independent Cell Adhesion Molecules [29:00]

The question asks about calcium-independent cell surface adhesion molecules (CAMs). While Catherin is calcium-dependent, the Ig superfamily is calcium-independent. Selectins and integrins are divalent cation-dependent, sometimes involving calcium.

Question 9: Transcription Activator Proteins [31:04]

Transcription activator proteins enhance the process of transcription. They do not bind to ribosomes to activate protein production (translation), transmit a message of a DNA template (RNA polymerase does this), or function during translation or tRNA function.

Question 10: Protein Synthesis Sequence [34:04]

The question requires arranging protein synthesis steps in the correct sequence. The correct order is initiation factor IF2, elongation factor thermo unstable, elongation factor G, release factor RF1, and ribosome recycling factor.

Question 11: Growth Factors and Cell Migration [38:57]

A growth factor activates RhoA, causing actin polymerization. The downstream event that explains enhanced cell migration is the depolymerization of cortical actin at the leading edge.

Question 12: Vesicular Transport and Protein Localization [42:24]

A protein required for vesicular transport, when fused to GFP, shows many small, round structures. This pattern is characteristic of Rab proteins, which are involved in vesicle targeting.

Question 13: Lac Operon and Partial Diploids [47:37]

The question involves analyzing partial diploids of the lac operon to determine which will have constitutive expression of beta-galactosidase. The correct answer involves a scenario where the operator is constitutive (OC) and the repressor is absent (I-), allowing for continuous expression despite the presence of a wild-type repressor gene in trans.

Question 14: Apoptosis Intrinsic Pathway [53:15]

The question requires arranging the events of the intrinsic apoptosis pathway in the correct sequence. The correct order is mitochondrial changes, apoptosome formation, caspase-9 activation, and caspase-3 activation.

Question 15: Transmembrane Proteins and Cell Characterization [57:39]

A membrane biologist elucidates the molecular structure of a protein that penetrates the lipid bilayer with several nonpolar, parallel alpha-helical segments. The most logical initial characterization is as a channel protein, due to the parallel arrangement facilitating pore formation.

Question 16: Phosphoglycerides [1:03:33]

Phosphoglycerides are composed of fatty acids, glycerol, phosphate, and alcohol. Membrane phosphoglycerides are typically diglycerides.

Question 17: DNA Polymerase Gamma and Mitochondrial DNA Replication [1:07:10]

DNA polymerase gamma is responsible for mitochondrial DNA replication. If mutated, it can lead to stalling and skipping of nucleotides, resulting in deletion mutations.

Question 18: Nucleosome Composition [1:07:10]

A nucleosome consists of an octameric complex of H2A, H2B, H3, and H4 histones with DNA wrapped around it. When linker histone H1 is associated, the structure is called a chromatosome.

Question 19: Experimental Setup and DNA Replication [1:13:37]

E. coli cells are grown with a transcription inhibitor, allowing only replication. After breaking the cells and treating the DNA with radioactively labeled antibodies against DNA ligase and DNA pol I, the highest concentration of these enzymes will be found on the lagging strand in both directions from the origin of replication.

Question 20: Connexin 43 and Gap Junctions [1:17:23]

In cultured astrocytes, silencing RNA against connexin 43 spreads to neighboring cells because the cells are already cultured and have established gap junctions.

Question 21: Heterochromatin and Replication Fork [1:26:42]

A eukaryotic replication fork slows down significantly when moving through a region of highly compact heterochromatin due to dense nucleosome packaging and reduced accessibility to the origin recognition complex (ORC).

Question 22: Lac Operon Mutation and Observations [1:32:48]

A bacterium with a mutation in the lac operator that prevents repressor binding will exhibit reduced beta-galactosidase production in glucose only, as glucose inhibits adenylate cyclase, reducing cAMP levels and catabolite repression.

Question 23: ATM and DNA Damage [1:40:30]

Cells deficient in ATM, a protein involved in DNA damage response, will exhibit a failure to detect double-stranded DNA breaks and a defective cell cycle arrest.

Question 24: Active Transporters [1:47:34]

Active transporters are identified by their use of ATP or coupling to ion gradients. Examples include ATPases, glucose transport by sodium-glucose symporters, and proton transport by sodium-proton antiporters.

Question 25: Protein Destination and Signal Peptides [1:54:30]

A protein destined for the lysosome lacking a signal peptide and containing a nuclear localization signal (NLS) will remain cytosolic.

Question 26: Protein Transport and Acidic Compartments [1:57:57]

A protein transport protein requiring ATP and resulting in an acidic pH is likely a vacuolar-type H+ ATPase, found in lysosomes.

Question 27: Cohesin and Chromosome Segregation [2:00:56]

A defect in cohesin removal during anaphase will most severely impact the accuracy of chromosome segregation.

Question 28: Glucose Transporters [2:03:21]

The correct statements about glucose transporters are that the sodium-potassium pump transports sodium out of the cell, GLUT uniporters transport glucose out of the cell, and the glucose concentration inside the cell is higher relative to the external environment.

Question 29: Chromatin Organization [2:05:54]

The correct order of chromatin organization is double-stranded DNA, nucleosome, solenoid, and chromosome.

Question 30: Acetylcholine and Neuronal Receptors [2:49:36]

The binding of acetylcholine to a neuronal receptor causes rapid depolarization through the opening of ligand-gated sodium channels.

Question 31: Membrane Fluidity and Cholesterol [2:54:57]

At low temperatures, membrane fluidity is reduced, and cholesterol counteracts this rigidification.

Question 32: Energy Requirements for Cellular Actions [2:59:46]

Actin filaments need energy from ATP, and microtubules need energy from GTP to perform their actions.

Question 33: EGF Receptor and Endocytosis [3:01:26]

If the EGF receptor remains constitutively active due to a failure in clathrin-mediated endocytosis, it will result in prolonged Ras activation and uncontrolled cell proliferation.

Question 34: DNA Polymerase I Activities [3:15:26]

DNA polymerase I is a multifunctional enzyme that promotes DNA synthesis, removes nucleotides from 3' termini in DNA, and removes nucleotides from 5' termini in DNA.

Question 35: Mushroom Poisoning and RNA Polymerase [3:18:30]

Liver failure due to poisoning from Amanita phalloides, which contains alpha-amanitin, is most likely due to the inhibition of mRNA synthesis.

Question 36: Enzyme Mechanisms and Intermediates [3:22:06]

The correct matches between enzymes, activated intermediates, and leaving groups are: DNA polymerase with activated dNTPs and pyrophosphate, DNA ligase with DNA adenylyl and AMP, and topoisomerase I with DNA tyrosyl.

Question 37: Nuclear Import and Ran GEF [3:26:44]

A GFP-tagged transcription factor with an NLS shows slowed nuclear import in cells expressing mutant Ran GEF. This is because Ran GTP accumulates in the nucleus, blocking importin release.

Question 38: Chromosome Number and DNA Content [3:31:49]

At the diplotene stage of meiosis I, the chromosome number is n, and the DNA content is 4C.

Question 39: DNA Repair Pathways [3:32:22]

Cells with BRCA1 knockout, when irradiated, show high 53BP1 and low Rad51 levels. This indicates that non-homologous end joining is the preferentially used repair pathway.

Question 40: Transcription Factors and Enhancers [3:34:38]

If a transcription factor is knocked out and ATAC sequencing shows decreased peaks across multiple enhancers, with corresponding decreases in H3K27 acetylation, it suggests that the transcription factor is a pioneer factor.

Question 41: Origin Licensing and DNA Replication [3:39:36]

If a mutant ORC complex binds an origin but cannot recruit MCM helicase, the most immediately affected process is origin licensing.

Question 42: DNA Replication Statements [3:43:34]

The correct statement about DNA replication is that leading and lagging strands are synthesized in different manners because the DNA strands are antiparallel.

Question 43: Mitochondrial Targeting Sequence [3:45:29]

A precursor protein lacking its mitochondrial targeting sequence (MTS) and engineered to contain a nuclear localization signal (NLS) will remain in the cytosol.

Question 44: Cohesin Removal and Anaphase [3:48:30]