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Question 1. Which scientist first coined the term “cell” after observing cork tissue under a microscope? A) Antonie van Leeuwenhoek B) Robert Hooke C) Matthias Schleiden D) Theodor Schwann Answer: B Explanation: Robert Hooke described the box‑like structures he saw in cork as “cells” in 1665. Question 2. The principle that all cells arise from pre‑existing cells was formulated by: A) Rudolf Virchow B) Matthias Schleiden C) Theodor Schwann D) Antonie van Leeuwenhoek Answer: A Explanation: Virchow’s “Omnis cellula e cellula” established that new cells originate only from existing cells. Question 3. Which of the following is NOT a modern addition to the original three pillars of cell theory? A) Energy flow occurs within cells. B) All cells contain a nucleus. C) DNA is passed from cell to cell. D) All cells share the same basic chemical composition. Answer: B Explanation: Modern cell theory recognizes that prokaryotes lack a membrane‑bound nucleus.
Question 4. Prokaryotic cells differ from eukaryotic cells because they: A) Possess mitochondria. B) Contain linear chromosomes. C) Lack a membrane‑bound nucleus. D) Have a well‑developed endoplasmic reticulum. Answer: C Explanation: Prokaryotes have a nucleoid region instead of a true nucleus. Question 5. Which structure is common to both prokaryotes and eukaryotes? A) Golgi apparatus B) Ribosomes C) Lysosomes D) Peroxisomes Answer: B Explanation: Ribosomes are present in all cells for protein synthesis, though their size differs. Question 6. In eukaryotic cells, the nucleolus is primarily responsible for: A) DNA replication B) Ribosomal RNA synthesis C) Protein folding D) Lipid synthesis Answer: B Explanation: The nucleolus transcribes rRNA and assembles ribosomal subunits.
Question 10. The inner membrane of mitochondria is folded into structures called: A) Cristae B) Thylakoids C) Lamellae D) Granules Answer: A Explanation: Cristae increase the surface area for oxidative phosphorylation. Question 11. In plant cells, the site of the light‑dependent reactions of photosynthesis is the: A) Stroma B) Thylakoid membrane C) Cytosol D) Mitochondrial matrix Answer: B Explanation: Light‑driven electron transport occurs in the thylakoid membranes. Question 12. Which cytoskeletal element is primarily responsible for chromosome movement during mitosis? A) Microfilaments B) Intermediate filaments C) Microtubules D) Actin filaments Answer: C Explanation: The mitotic spindle is composed of microtubules that segregate chromosomes.
Question 13. The fluid mosaic model of the plasma membrane emphasizes that: A) Membrane proteins are static. B) Lipids are arranged in a rigid lattice. C) Both lipids and proteins can move laterally. D) Carbohydrates are the main structural component. Answer: C Explanation: The model describes a dynamic, fluid bilayer with moving proteins and lipids. Question 14. Which type of transport requires no energy input and moves solutes down their concentration gradient? A) Primary active transport B) Facilitated diffusion C) Secondary active transport D) Endocytosis Answer: B Explanation: Facilitated diffusion uses carrier or channel proteins but does not require ATP. Question 15. The Na⁺/K⁺‑ATPase pump moves ions in which direction per cycle? A) 3 Na⁺ out, 2 K⁺ in B) 2 Na⁺ out, 3 K⁺ in C) 3 Na⁺ in, 2 K⁺ out D) 2 Na⁺ in, 3 K⁺ out Answer: A Explanation: The pump exports three sodium ions and imports two potassium ions, using one ATP.
A) Ambient magnetic field B) pH of the environment C) Color of the solution D) Atmospheric pressure Answer: B Explanation: Enzymes have optimal pH ranges; deviations alter active‑site ionization. Question 20. In glycolysis, the net production of ATP per glucose molecule is: A) 2 ATP B) 4 ATP C) 6 ATP D) 8 ATP Answer: A Explanation: Glycolysis consumes 2 ATP and produces 4, yielding a net gain of 2 ATP. Question 21. The citric acid cycle occurs in the: A) Cytosol B) Mitochondrial matrix C) Inner mitochondrial membrane D) Endoplasmic reticulum Answer: B Explanation: All enzymes of the Krebs cycle are located in the mitochondrial matrix. Question 22. Which electron carrier donates electrons to Complex IV of the electron transport chain?
A) NADH
B) FADH₂
C) Cytochrome c D) Coenzyme Q (ubiquinone) Answer: C Explanation: Cytochrome c transfers electrons from Complex III to Complex IV. Question 23. During the light‑independent (Calvin) cycle, CO₂ is fixed into which three‑carbon compound? A) Glucose B) Glyceraldehyde‑ 3 ‑phosphate C) Ribulose‑1,5‑bisphosphate D) 3‑Phosphoglycerate Answer: D Explanation: CO₂ combines with ribulose‑1,5‑bisphosphate to form 3‑phosphoglycerate. Question 24. Which checkpoint monitors DNA integrity before a cell enters S phase? A) G1 checkpoint B) G2 checkpoint C) M checkpoint D) Spindle checkpoint Answer: A Explanation: The G1 checkpoint ensures conditions are favorable and DNA is undamaged before replication.
Question 28. Meiosis reduces the chromosome number from diploid to haploid. How many rounds of DNA replication occur? A) One B) Two C) Three D) None Answer: A Explanation: DNA replicates only once before Meiosis I; subsequent divisions separate sister chromatids without further replication. Question 29. Crossing over occurs during which meiotic stage? A) Prophase I – pachytene B) Metaphase I C. Anaphase II D) Telophase I Answer: A Explanation: Homologous chromosomes exchange genetic material during pachytene of prophase I. Question 30. Autocrine signaling involves: A) Hormones traveling through the bloodstream. B) A cell responding to its own secreted signal. C) Direct membrane‑to‑membrane contact. D) Signals acting on neighboring cells only. Answer: B Explanation: In autocrine signaling, the secreting cell also possesses receptors for its own ligand.
Question 31. Which second messenger is most commonly associated with G‑protein‑coupled receptor activation? A) cAMP B) DNA C) ATP D) NAD⁺ Answer: A Explanation: Adenylyl cyclase converts ATP to cyclic AMP upon GPCR stimulation. Question 32. Apoptosis is essential for: A) Uncontrolled cell proliferation. B) Removing damaged or unnecessary cells. C) Generating ATP. D) Maintaining plasma membrane rigidity. Answer: B Explanation: Programmed cell death eliminates cells that could become harmful or are no longer needed. Question 33. Which of the following best describes a plasmid? A) A linear chromosome in eukaryotes. B. A small, circular DNA molecule in prokaryotes. C. A membrane‑bound organelle. D. A ribosomal subunit. Answer: B
Explanation: Ribosomes on the rough ER translate mRNA encoding proteins destined for secretion or membranes. Question 37. Which protein structure spans the plasma membrane and forms a channel for passive ion flow? A. Integral membrane protein B. Peripheral membrane protein C. Cytoskeletal protein D. Extracellular matrix protein Answer: A Explanation: Integral proteins often contain transmembrane domains that create channels. Question 38. A cell that lacks a cell wall and has a flexible plasma membrane is most likely: A. A plant cell B. A bacterial cell C. An animal cell D. A fungal cell Answer: C Explanation: Animal cells do not possess rigid cell walls, unlike plant, bacterial, or fungal cells. Question 39. Which of the following processes is directly coupled to the hydrolysis of ATP? A. Facilitated diffusion of glucose B. Primary active transport by the Na⁺/K⁺ pump C. Simple diffusion of oxygen D. Osmosis of water
Answer: B Explanation: Primary active transport uses ATP directly to move ions against their gradient. Question 40. The mitochondrial matrix enzyme pyruvate dehydrogenase converts pyruvate into: A. Acetyl‑CoA B. Oxaloacetate C. Lactic acid D. Citrate Answer: A Explanation: Pyruvate dehydrogenase links glycolysis to the Krebs cycle by forming acetyl‑CoA. Question 41. In the electron transport chain, the final electron acceptor in aerobic respiration is: A. NAD⁺ B. FAD C. Oxygen D. Carbon dioxide Answer: C Explanation: Molecular O₂ accepts electrons at Complex IV, forming water. Question 42. Which of the following statements about peroxisomes is true? A. They generate ATP via oxidative phosphorylation. B. They contain DNA. C. They oxidize very long‑chain fatty acids. D. They are exclusive to plant cells. Answer: C
Explanation: Pinocytosis (“cell drinking”) engulfs fluid without large particles. Question 46. Which of the following best describes the role of microfilaments? A. Forming the mitotic spindle B. Providing tensile strength to the cell cortex C. Transporting vesicles along axons D. Anchoring the nucleus Answer: B Explanation: Actin microfilaments generate contractile forces and maintain cell shape. Question 47. In the context of signal transduction, a ligand that binds to a receptor tyrosine kinase typically causes: A. Immediate opening of ion channels. B. Dimerization and autophosphorylation of the receptor. C. Direct activation of G‑proteins. D. Production of cyclic GMP. Answer: B Explanation: RTKs dimerize upon ligand binding, leading to autophosphorylation and downstream signaling. Question 48. Which of the following is a characteristic of the S phase of the cell cycle? A. Chromosome condensation B. DNA replication C. Cytokinesis D. Spindle assembly
Answer: B Explanation: The S (synthesis) phase is dedicated to copying the genome. Question 49. Which organelle is primarily responsible for the synthesis of steroid hormones? A. Mitochondrion B. Smooth ER C. Golgi apparatus D. Lysosome Answer: B Explanation: Steroidogenesis occurs in the smooth endoplasmic reticulum. Question 50. The term “turgor pressure” refers to: A. The pressure exerted by the cell wall on the plasma membrane. B. The osmotic pressure inside animal cells. C. The pressure of the cytoplasm against the cell membrane in plant cells. D. The pressure generated by mitochondria during ATP synthesis. Answer: C Explanation: Turgor pressure is the outward force exerted by the vacuole‑filled cytoplasm against the cell wall. Question 51. Which of the following best describes a “symporter”? A. Moves two substances in opposite directions. B. Moves one substance without using energy. C. Couples the downhill movement of one solute with the uphill movement of another. D. Pumps ions using ATP directly.
D. O₂
Answer: B Explanation: Water is split (photolysis) to provide electrons, producing O₂ as a by‑product. Question 55. In a cell undergoing apoptosis, which of the following morphological changes is typical? A. Cell swelling and plasma membrane rupture. B. Chromatin condensation and formation of apoptotic bodies. C. Formation of a large multinucleated cell. D. Immediate DNA replication. Answer: B Explanation: Apoptosis features nuclear fragmentation, chromatin condensation, and membrane blebbing into apoptotic bodies. Question 56. Which of the following best describes the role of the “spindle checkpoint”? A. Ensures DNA replication is complete before mitosis. B. Monitors attachment of kinetochores to spindle microtubules. C. Checks for proper cytokinesis. D. Verifies cell size before entering S phase. Answer: B Explanation: The spindle checkpoint prevents anaphase onset until all chromosomes are correctly attached. Question 57. The enzyme DNA polymerase adds nucleotides to a growing DNA strand in the: A. 3’ → 5’ direction. B. 5’ → 3’ direction.
C. Both directions simultaneously. D. Random direction. Answer: B Explanation: DNA polymerases synthesize DNA only in the 5’ to 3’ direction. Question 58. Which of the following is a characteristic of a plant cell’s vacuole? A. Stores genetic material. B. Generates ATP. C. Maintains turgor and stores metabolites. D. Synthesizes proteins. Answer: C Explanation: The central vacuole provides osmotic balance, stores ions, and contributes to cell rigidity. Question 59. Which of the following processes requires the hydrolysis of GTP rather than ATP? A. Protein synthesis on ribosomes. B. Tubulin polymerization during spindle formation. C. Sodium‑potassium pump activity. D. DNA helicase unwinding. Answer: B Explanation: Tubulin binds GTP; its polymerization into microtubules involves GTP hydrolysis. Question 60. In the context of membrane proteins, “glycosylation” most commonly occurs on which part of the protein? A. Cytoplasmic domain B. Transmembrane domain
