1. Who proposed the classic generalization “Omnis cellula-e cellula” (all cells arise from pre-existing cells)?
Correct Answer: B (Rudolf Virchow)
Rudolf Virchow (1855) first explained that cells divide and new cells are formed from pre-existing cells (*Omnis cellula-e cellula*), modifying the cell theory.
Rudolf Virchow (1855) first explained that cells divide and new cells are formed from pre-existing cells (*Omnis cellula-e cellula*), modifying the cell theory.
2. According to the Fluid Mosaic Model proposed by Singer and Nicolson (1972), the quasi-fluid nature of membrane lipids enables:
Correct Answer: A (Lateral movement of proteins within the overall bilayer)
The quasi-fluid nature of the lipid bilayer allows lateral diffusion of proteins, defining membrane fluidity essential for cell growth, secretion, and endocytosis.
The quasi-fluid nature of the lipid bilayer allows lateral diffusion of proteins, defining membrane fluidity essential for cell growth, secretion, and endocytosis.
3. Which of the following organelles is NOT part of the endomembrane system?
Correct Answer: D (Mitochondria, Chloroplasts, and Peroxisomes)
The endomembrane system includes ER, Golgi, lysosomes, and vacuoles because their functions are coordinated. Mitochondria, chloroplasts, and peroxisomes are not coordinated with these and are excluded.
The endomembrane system includes ER, Golgi, lysosomes, and vacuoles because their functions are coordinated. Mitochondria, chloroplasts, and peroxisomes are not coordinated with these and are excluded.
4. The smooth endoplasmic reticulum (SER) is the major site for the synthesis of:
Correct Answer: B (Lipids, phospholipids, and steroid hormones)
RER synthesizes proteins, whereas SER synthesizes lipids, triglycerides, and steroid hormones (like testosterone and estrogen) in animal cells.
RER synthesizes proteins, whereas SER synthesizes lipids, triglycerides, and steroid hormones (like testosterone and estrogen) in animal cells.
5. What is the primary function of the Golgi apparatus?
Correct Answer: B (Post-translational modification, packaging, and sorting of proteins and lipids)
Proteins synthesized by the ER fuse with the *cis* face of the Golgi cisternae, undergo glycosylation to form glycoproteins/glycolipids, and exit from the *trans* face.
Proteins synthesized by the ER fuse with the *cis* face of the Golgi cisternae, undergo glycosylation to form glycoproteins/glycolipids, and exit from the *trans* face.
6. Lysosomal hydrolytic enzymes (hydrolases) are optimally active at which pH?
Correct Answer: A (Acidic pH (~ 5.0))
Lysosomal acid hydrolases (lipases, proteases, nucleases) function optimally at acidic pH maintained by membrane proton (H+) pumps.
Lysosomal acid hydrolases (lipases, proteases, nucleases) function optimally at acidic pH maintained by membrane proton (H+) pumps.
7. In plant cells, the central vacuole is bounded by a single semi-permeable membrane called:
Correct Answer: B (Tonoplast)
The tonoplast actively pumps ions and solutes against concentration gradients into the vacuole, maintaining plant cellular turgor pressure.
The tonoplast actively pumps ions and solutes against concentration gradients into the vacuole, maintaining plant cellular turgor pressure.
8. Infoldings of the inner mitochondrial membrane that increase the surface area for ATP synthase complexes are called:
Correct Answer: B (Cristae)
Cristae are inner mitochondrial membrane foldings studded with oxysomes (F0-F1 particles) for oxidative phosphorylation.
Cristae are inner mitochondrial membrane foldings studded with oxysomes (F0-F1 particles) for oxidative phosphorylation.
9. What type of ribosomes are found in prokaryotes, mitochondria, and chloroplasts versus eukaryotic cytoplasm?
Correct Answer: A (70S (50S + 30S) and 80S (60S + 40S) respectively)
Prokaryotic, mitochondrial, and plastid ribosomes are 70S (subunits 50S and 30S), while eukaryotic cytoplasmic ribosomes are 80S (subunits 60S and 40S).
Prokaryotic, mitochondrial, and plastid ribosomes are 70S (subunits 50S and 30S), while eukaryotic cytoplasmic ribosomes are 80S (subunits 60S and 40S).
10. Colorless plastids that primarily store nutrients such as starch, oils, and proteins are called:
Correct Answer: C (Leucoplasts)
Leucoplasts store reserves: Amyloplasts store carbohydrates (starch), Elaioplasts store oils/fats, and Aleuroplasts store proteins.
Leucoplasts store reserves: Amyloplasts store carbohydrates (starch), Elaioplasts store oils/fats, and Aleuroplasts store proteins.
11. The microtubular arrangement in the axoneme of eukaryotic cilia and flagella is:
Correct Answer: A (9 + 2 arrangement (9 doublets + 2 central singlets))
Cilia and flagella axonemes possess 9 peripheral paired doublets and 2 central single microtubules (9+2), whereas centrioles and basal bodies have a cartwheel-like 9+0 triplet pattern.
Cilia and flagella axonemes possess 9 peripheral paired doublets and 2 central single microtubules (9+2), whereas centrioles and basal bodies have a cartwheel-like 9+0 triplet pattern.
12. The site for active synthesis of ribosomal RNA (rRNA) inside the nucleus is the:
Correct Answer: B (Nucleolus)
The nucleolus is a non-membrane bound subnuclear structure dedicated to the transcription and assembly of ribosomal RNA subunits.
The nucleolus is a non-membrane bound subnuclear structure dedicated to the transcription and assembly of ribosomal RNA subunits.
13. A chromosome with the centromere positioned extremely close to one end, resulting in one extremely short and one very long arm, is classified as:
Correct Answer: C (Acrocentric)
Acrocentric chromosomes have a sub-terminal centromere forming one minute short arm and one long arm. Telocentric chromosomes have a terminal centromere.
Acrocentric chromosomes have a sub-terminal centromere forming one minute short arm and one long arm. Telocentric chromosomes have a terminal centromere.
14. Middle lamella that cements adjacent plant cell walls together is primarily composed of:
Correct Answer: A (Calcium and magnesium pectate)
The middle lamella is an amorphous intercellular layer made mainly of calcium and magnesium pectate that holds neighbouring plant cells together.
The middle lamella is an amorphous intercellular layer made mainly of calcium and magnesium pectate that holds neighbouring plant cells together.
15. In prokaryotic cells, mesosomes are specialized membranous infoldings of the plasma membrane that function in:
Correct Answer: B (Cell wall formation, DNA replication, and cellular respiration)
Mesosomes increase surface area for enzymatic activities, aid in cellular respiration, secretion, cell wall synthesis, and chromosome replication/distribution.
Mesosomes increase surface area for enzymatic activities, aid in cellular respiration, secretion, cell wall synthesis, and chromosome replication/distribution.
16. Microbodies containing catalase and urate oxidase involved in photorespiration in plants and lipid metabolism in animals are:
Correct Answer: A (Peroxisomes)
Peroxisomes are single-membrane microbodies containing enzymes that convert hydrogen peroxide (H2O2) to water and participate in glycolate metabolism during plant photorespiration.
Peroxisomes are single-membrane microbodies containing enzymes that convert hydrogen peroxide (H2O2) to water and participate in glycolate metabolism during plant photorespiration.
17. When plant or animal tissue is ground in Trichloroacetic acid (Cl3CCOOH) and filtered, which fraction contains biomacromolecules (proteins, nucleic acids, polysaccharides)?
Correct Answer: B (Acid-insoluble pool (retentate))
Macromolecules with molecular weights >1000 Da (proteins, polysaccharides, nucleic acids, and lipid aggregates) are retained on the filter as the acid-insoluble retentate.
Macromolecules with molecular weights >1000 Da (proteins, polysaccharides, nucleic acids, and lipid aggregates) are retained on the filter as the acid-insoluble retentate.
18. Why are lipids, despite having molecular weights not exceeding 800 Da, found in the acid-insoluble macromolecular fraction?
Correct Answer: A (They form large hydrophobic insoluble vesicle aggregates/micelles during tissue disruption)
Lipids are not strict polymers, but cell membrane fragments assemble into water-insoluble vesicular aggregates that do not pass through the filter cloth.
Lipids are not strict polymers, but cell membrane fragments assemble into water-insoluble vesicular aggregates that do not pass through the filter cloth.
19. Which of the following is a secondary metabolite categorized as an alkaloid?
Correct Answer: B (Morphine and Codeine)
Morphine/Codeine are alkaloids; Concanavalin A is a lectin; Abrin/Ricin are toxins; Carotenoids/Anthocyanins are pigments.
Morphine/Codeine are alkaloids; Concanavalin A is a lectin; Abrin/Ricin are toxins; Carotenoids/Anthocyanins are pigments.
20. Which of the following is an example of a polymeric secondary metabolite?
Correct Answer: C (Rubber, Gums, and Cellulose)
Rubber, gums, and cellulose are classed as polymeric secondary metabolites according to NCERT classifications.
Rubber, gums, and cellulose are classed as polymeric secondary metabolites according to NCERT classifications.
21. The most abundant protein in the whole of the biosphere and in the animal world respectively are:
Correct Answer: A (RuBisCO and Collagen)
Collagen is the most abundant protein in animals, while Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO) is the most abundant protein in the entire biosphere.
Collagen is the most abundant protein in animals, while Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO) is the most abundant protein in the entire biosphere.
22. What bond joins adjacent nucleotides in a polynucleotide chain (DNA/RNA)?
Correct Answer: B (3′-5′ Phosphodiester bond)
Nucleotides are joined by a phosphodiester linkage between the 3′-OH group of one pentose sugar and the 5′-phosphate group of the adjoining nucleotide.
Nucleotides are joined by a phosphodiester linkage between the 3′-OH group of one pentose sugar and the 5′-phosphate group of the adjoining nucleotide.
23. In the B-DNA double helix model of Watson and Crick, the pitch of the helix and the distance between adjacent base pairs are:
Correct Answer: A (34 Å (3.4 nm) and 3.4 Å (0.34 nm) respectively)
Each complete helical turn has 10 base pairs, spanning a pitch of 3.4 nm (34 Å), giving a rise per base pair of 0.34 nm (3.4 Å).
Each complete helical turn has 10 base pairs, spanning a pitch of 3.4 nm (34 Å), giving a rise per base pair of 0.34 nm (3.4 Å).
24. Adenosine, Guanosine, Cytidine, and Uridine are examples of:
Correct Answer: B (Nucleosides)
A nitrogenous base attached to a ribose or deoxyribose sugar is a nucleoside. When phosphorylated, it becomes a nucleotide (e.g., adenylic acid).
A nitrogenous base attached to a ribose or deoxyribose sugar is a nucleoside. When phosphorylated, it becomes a nucleotide (e.g., adenylic acid).
25. How do enzymes accelerate the rates of chemical reactions?
Correct Answer: B (Lowering the activation energy required to reach the transition state)
Enzymes stabilize the transient transition-state intermediate, drastically lowering the activation energy barrier without altering overall net free energy change ($\Delta G$).
Enzymes stabilize the transient transition-state intermediate, drastically lowering the activation energy barrier without altering overall net free energy change ($\Delta G$).
26. Malonate closely resembles succinate in structure and competitively inhibits which enzyme?
Correct Answer: A (Succinate dehydrogenase)
Malonate competes with substrate succinate for the catalytic active site of succinate dehydrogenase, demonstrating competitive enzyme inhibition.
Malonate competes with substrate succinate for the catalytic active site of succinate dehydrogenase, demonstrating competitive enzyme inhibition.
27. How does a competitive inhibitor affect the kinetic parameters Km (Michaelis constant) and Vmax of an enzyme?
Correct Answer: A (Km increases, while Vmax remains unchanged)
Because high substrate concentrations can outcompete the inhibitor, maximum velocity ($V_{\max}$) is reached, but the apparent affinity is reduced (higher $K_m$).
Because high substrate concentrations can outcompete the inhibitor, maximum velocity ($V_{\max}$) is reached, but the apparent affinity is reduced (higher $K_m$).
28. A non-protein organic cofactor that is firmly and tightly bound to the apoenzyme is called a:
Correct Answer: A (Prosthetic group)
Prosthetic groups (e.g., haem in catalase and peroxidase) are permanently and tightly bound to the protein apoenzyme. Coenzymes are transiently bound.
Prosthetic groups (e.g., haem in catalase and peroxidase) are permanently and tightly bound to the protein apoenzyme. Coenzymes are transiently bound.
29. Enzymes that catalyze the linking together of two compounds (e.g., C-O, C-S, C-N, or C-C bonds) utilizing ATP belong to Class:
Correct Answer: C (Ligases)
Class 6 enzymes are Ligases (synthetases), which catalyze the covalent joining of two molecules coupled with high-energy pyrophosphate hydrolysis.
Class 6 enzymes are Ligases (synthetases), which catalyze the covalent joining of two molecules coupled with high-energy pyrophosphate hydrolysis.
30. Which metallic cofactor is essential for the catalytic activity of Carboxypeptidase?
Correct Answer: B (Zinc (Zn2+))
Zinc is a coordinated metal cofactor essential for the proteolytic digestive enzyme carboxypeptidase.
Zinc is a coordinated metal cofactor essential for the proteolytic digestive enzyme carboxypeptidase.
31. In the eukaryotic cell cycle, replication of nuclear genomic DNA and duplication of centrioles in the cytoplasm occur during:
Correct Answer: B (S (Synthesis) phase)
During S phase, the amount of DNA per cell doubles from 2C to 4C (chromosome number remaining 2n), and centrioles duplicate in the cytoplasm of animal cells.
During S phase, the amount of DNA per cell doubles from 2C to 4C (chromosome number remaining 2n), and centrioles duplicate in the cytoplasm of animal cells.
32. The quiescent stage (G0 phase) of the cell cycle refers to cells that:
Correct Answer: B (Exit the cell cycle and remain metabolically active without proliferating)
Cells in G0 (e.g., adult heart cells, neurons) exit the cell cycle; they remain metabolically active but divide only when called upon to replace injured tissue.
Cells in G0 (e.g., adult heart cells, neurons) exit the cell cycle; they remain metabolically active but divide only when called upon to replace injured tissue.
33. If an initial diploid root cell has 2C DNA content and 14 chromosomes at G1, what will be the DNA content and chromosome number after S phase?
Correct Answer: B (4C and 14)
DNA replication doubles the total amount of DNA (2C → 4C), but chromosome number remains unchanged (14 chromosomes, each now composed of two sister chromatids).
DNA replication doubles the total amount of DNA (2C → 4C), but chromosome number remains unchanged (14 chromosomes, each now composed of two sister chromatids).
34. During which stage of mitotic prophase do the nuclear envelope, nucleolus, Golgi complex, and ER completely disassemble?
Correct Answer: B (End of prophase (Late prophase))
At the end of prophase, when viewed under the microscope, cells do not show nucleolus, nuclear envelope, ER, or Golgi complexes.
At the end of prophase, when viewed under the microscope, cells do not show nucleolus, nuclear envelope, ER, or Golgi complexes.
35. The morphology and size of chromosomes are best studied at which mitotic stage?
Correct Answer: B (Metaphase)
At metaphase, chromosomal condensation is maximal and chromosomes align symmetrically along the equatorial metaphase plate, making morphological analysis ideal.
At metaphase, chromosomal condensation is maximal and chromosomes align symmetrically along the equatorial metaphase plate, making morphological analysis ideal.
36. Small disc-shaped protein complexes situated on the surface of the centromere to which spindle fibres attach are called:
Correct Answer: A (Kinetochores)
Kinetochores are trilaminar protein assemblies that serve as points of attachment for spindle microtubules to pull chromatids apart.
Kinetochores are trilaminar protein assemblies that serve as points of attachment for spindle microtubules to pull chromatids apart.
37. Splitting of centromeres and synchronous poleward migration of sister chromatids (now individual daughter chromosomes) occur during:
Correct Answer: B (Anaphase)
During anaphase, centromeres split simultaneously, allowing kinetochore microtubule shortening to pull individual daughter chromosomes to opposite poles (forming V, L, J, or I shapes).
During anaphase, centromeres split simultaneously, allowing kinetochore microtubule shortening to pull individual daughter chromosomes to opposite poles (forming V, L, J, or I shapes).
38. Plant cytokinesis differs from animal cytokinesis because plant cells divide via:
Correct Answer: B (Centrifugal cell plate (Phragmoplast) formation)
Because plant cells have rigid inextensible walls, Golgi-derived vesicles aggregate in the center to form a cell plate that grows centrifugally outwards to meet lateral walls.
Because plant cells have rigid inextensible walls, Golgi-derived vesicles aggregate in the center to form a cell plate that grows centrifugally outwards to meet lateral walls.
39. The liquid endosperm of coconut is a multinucleated syncytium formed due to:
Correct Answer: B (Repeated karyokinesis not followed by cytokinesis)
When nuclear division (karyokinesis) proceeds repeatedly in the absence of cell division (cytokinesis), a coenocytic or syncytial condition results (e.g., coconut liquid endosperm).
When nuclear division (karyokinesis) proceeds repeatedly in the absence of cell division (cytokinesis), a coenocytic or syncytial condition results (e.g., coconut liquid endosperm).
40. Synapsis—the pairing of homologous chromosomes mediated by the synaptonemal complex—occurs during which substage of Meiotic Prophase I?
Correct Answer: B (Zygotene)
During zygotene, homologous chromosomes pair together (synapsis) assisted by a proteinaceous synaptonemal complex, forming bivalents (tetrads).
During zygotene, homologous chromosomes pair together (synapsis) assisted by a proteinaceous synaptonemal complex, forming bivalents (tetrads).
41. Crossing over (genetic recombination between non-sister chromatids of homologous chromosomes) occurs during which stage and is mediated by which enzyme?
Correct Answer: B (Pachytene; Recombinase enzyme complex)
In pachytene, recombination nodules appear where crossing over occurs between non-sister chromatids of bivalents, catalyzed by recombinase.
In pachytene, recombination nodules appear where crossing over occurs between non-sister chromatids of bivalents, catalyzed by recombinase.
42. Dissolution of the synaptonemal complex and appearance of X-shaped cross-over attachment points (Chiasmata) characterize:
Correct Answer: B (Diplotene)
In diplotene, the synaptonemal complex dissolves and homologous chromosomes separate except at sites of crossovers, forming X-shaped chiasmata. (Oocytes of some vertebrates remain arrested in diplotene for months/years).
In diplotene, the synaptonemal complex dissolves and homologous chromosomes separate except at sites of crossovers, forming X-shaped chiasmata. (Oocytes of some vertebrates remain arrested in diplotene for months/years).
43. Terminalization of chiasmata and full condensation of meiotic chromosomes mark the final substage of Prophase I known as:
Correct Answer: C (Diakinesis)
Diakinesis is the terminal phase of prophase I where chiasmata shift to chromosome tips (terminalization), nucleolus vanishes, and spindle assembly prepares for Metaphase I.
Diakinesis is the terminal phase of prophase I where chiasmata shift to chromosome tips (terminalization), nucleolus vanishes, and spindle assembly prepares for Metaphase I.
44. In Anaphase I of Meiosis, which event takes place?
Correct Answer: A (Homologous chromosomes separate while sister chromatids remain attached at their centromeres)
Anaphase I is reductional: homologous chromosomes separate to opposite poles without centromere splitting. Centromere division occurs only in Anaphase II.
Anaphase I is reductional: homologous chromosomes separate to opposite poles without centromere splitting. Centromere division occurs only in Anaphase II.
45. The brief resting interval between Meiosis I and Meiosis II without intervening DNA replication is called:
Correct Answer: B (Interkinesis)
Interkinesis is a short-lived phase between telophase I and prophase II; no DNA replication ($S$ phase) occurs during interkinesis.
Interkinesis is a short-lived phase between telophase I and prophase II; no DNA replication ($S$ phase) occurs during interkinesis.
46. What chemical mitotic inhibitor arrests cells in metaphase by preventing microtubule polymerization and spindle formation?
Correct Answer: A (Colchicine)
Colchicine (extracted from *Colchicum autumnale*) binds tubulin dimers to inhibit mitotic spindle assembly, arresting cells at metaphase and inducing polyploidy.
Colchicine (extracted from *Colchicum autumnale*) binds tubulin dimers to inhibit mitotic spindle assembly, arresting cells at metaphase and inducing polyploidy.
47. A typical animal cell contains centrosomes which feature two mutually perpendicular cylindrical structures called:
Correct Answer: B (Centrioles)
The centrosome consists of two perpendicular centrioles surrounded by amorphous pericentriolar material; each centriole exhibits a 9+0 peripheral triplet cartwheel organization.
The centrosome consists of two perpendicular centrioles surrounded by amorphous pericentriolar material; each centriole exhibits a 9+0 peripheral triplet cartwheel organization.
48. Which structural polysaccharide of plant cell walls is a homopolymer of beta-D-glucose linked via beta-1,4-glycosidic bonds?
Correct Answer: C (Cellulose)
Cellulose is a linear, unbranched homopolysaccharide composed exclusively of $\beta$-D-glucose units connected by $\beta$-(1$\rightarrow$4) glycosidic bonds.
Cellulose is a linear, unbranched homopolysaccharide composed exclusively of $\beta$-D-glucose units connected by $\beta$-(1$\rightarrow$4) glycosidic bonds.
49. Chromatin contains DNA, basic proteins called histones, non-histone proteins, and RNA. The core histone octamer consists of two copies of each of:
Correct Answer: A (H2A, H2B, H3, and H4)
The nucleosome core particle comprises an octamer of basic histone proteins: two each of H2A, H2B, H3, and H4 wrapped around ~146 base pairs of DNA. Histone H1 serves as the linker.
The nucleosome core particle comprises an octamer of basic histone proteins: two each of H2A, H2B, H3, and H4 wrapped around ~146 base pairs of DNA. Histone H1 serves as the linker.
50. During which stage of the cell cycle do nuclear envelope reassembly, chromosome uncoiling into chromatin, and nucleolar reappearance occur?
Correct Answer: C (Telophase)
Telophase reverses the events of prophase: chromosomes decondense at opposite spindle poles, nuclear envelopes reform, and nucleolus, Golgi, and ER reappear.
Telophase reverses the events of prophase: chromosomes decondense at opposite spindle poles, nuclear envelopes reform, and nucleolus, Golgi, and ER reappear.