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and Function Ultimate Exam
Question 1. Which scientist first coined the term “cell” after observing cork tissue? A) Antonie van Leeuwenhoek B) Robert Hooke C) Matthias Schleiden D) Theodor Schwann Answer: B Explanation: Robert Hooke described the “cells” of cork in 1665, giving the name to the basic structural unit of life. Question 2. The statement “All cells arise from pre-existing cells” is attributed to which biologist? A) Rudolf Virchow B) Matthias Schleiden C) Theodor Schwann D) Louis Pasteur Answer: A Explanation: Virchow’s principle “Omnis cellula e cellula” (1845) asserts that new cells are produced only by division of existing cells. Question 3. Which of the following is NOT a component of the modern cell theory? A) Cells contain DNA that is passed to daughter cells. B) All cells have a plasma membrane. C) Cells can arise spontaneously from non-living matter. D) Energy metabolism occurs within cells. Answer: C Explanation: Modern cell theory rejects spontaneous generation; cells arise only from pre-existing cells. Question 4. In prokaryotes, the genetic material is organized as a:
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A) Linear chromosome within a nucleus B) Circular nucleoid without a membrane C) Multiple linear chromosomes in the cytoplasm D) Plasmid-only genome Answer: B Explanation: Prokaryotic DNA is a single circular chromosome located in the nucleoid region, not bounded by a membrane. Question 5. Which structure is common to both prokaryotic and eukaryotic cells? A) Endoplasmic reticulum B) Ribosomes C) Mitochondria D) Golgi apparatus Answer: B Explanation: Ribosomes, the sites of protein synthesis, are present in all cells, though their size differs (70S vs. 80S). Question 6. The primary function of the nucleolus is to: A) Store calcium ions B) Synthesize ribosomal RNA C) Package DNA into chromosomes D) Regulate cell cycle checkpoints Answer: B Explanation: The nucleolus assembles ribosomal subunits by transcribing rRNA and combining it with proteins. Question 7. Which organelle is responsible for lipid synthesis and detoxification of drugs? A) Rough endoplasmic reticulum
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C) Glutathione peroxidase D) Cytochrome c oxidase Answer: B Explanation: Catalase converts H₂O₂ into water and oxygen, preventing oxidative damage. Question 11. The inner mitochondrial membrane contains: A) DNA that codes for all mitochondrial proteins B) Numerous ribosomes for protein synthesis C) The electron transport chain complexes D) Large pores allowing free diffusion of ions Answer: C Explanation: The inner membrane houses the ETC complexes I-IV and ATP synthase, essential for oxidative phosphorylation. Question 12. Which pigment captures light energy in the thylakoid membranes of chloroplasts? A) Carotene B) Chlorophyll a C) Phycobilin D) Anthocyanin Answer: B Explanation: Chlorophyll a is the primary photosynthetic pigment that absorbs blue and red light for energy conversion. Question 13. Microtubules are assembled from which protein subunit? A) Actin monomers B) Tubulin dimers C) Intermediate filament proteins D) Myosin heads
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Answer: B Explanation: α- and β-tubulin dimers polymerize to form hollow microtubules. Question 14. Which cytoskeletal element is most directly involved in muscle contraction? A) Microtubules B) Intermediate filaments C) Actin filaments D) Centrioles Answer: C Explanation: Actin filaments interact with myosin to generate contractile force in muscle cells. Question 15. The fluid-mosaic model of the plasma membrane includes all EXCEPT: A) Phospholipid bilayer B) Integral proteins that span the membrane C) Covalently bound rigid carbohydrate lattice D) Cholesterol that modulates fluidity Answer: C Explanation: Carbohydrates are attached to lipids or proteins, not forming a rigid lattice. Question 16. Simple diffusion of oxygen across a cell membrane is driven primarily by: A ATP hydrolysis B Concentration gradient C Carrier proteins D Electrical potential Answer: B
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Question 20. A symporter that moves glucose into a cell using the Na⁺ gradient is an example of: A) Primary active transport B) Secondary active transport (cotransport) C) Facilitated diffusion D) Endocytosis Answer: B Explanation: The Na⁺ gradient (established by primary active transport) drives glucose uptake via a Na⁺/glucose symporter. Question 21. During pinocytosis, the cell primarily ingests: A) Large particles >0.5 μm B) Fluid and dissolved solutes C) DNA fragments D) Whole bacteria Answer: B Explanation: Pinocytosis (“cell drinking”) involves the uptake of extracellular fluid and small solutes. Question 22. Exocytosis is essential for: A) Importing nutrients B) Releasing neurotransmitters C) Phagocytosing pathogens D) Maintaining membrane potential Answer: B Explanation: Secretory vesicles fuse with the plasma membrane to release neurotransmitters, hormones, and enzymes. Question 23. Which law of thermodynamics states that energy cannot be created or destroyed?
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A) First law B) Second law C) Third law D) Zeroth law Answer: A Explanation: The first law (conservation of energy) applies to cellular metabolism; energy is transformed, not created. Question 24. ATP is considered the “energy currency” of the cell because: A) It stores energy in high-energy phosphate bonds. B) It is the only molecule that can be hydrolyzed. C) It contains double-stranded DNA. D) It is permanently bound to enzymes. Answer: A Explanation: Hydrolysis of the terminal phosphate releases ~7.3 kcal/mol, providing usable energy for cellular work. Question 25. Enzyme activity is maximally increased when the substrate concentration: A) Is zero B) Is at the Km value C) Exceeds Vmax D) Is saturating, reaching Vmax Answer: D Explanation: At saturating substrate levels, all active sites are occupied, and the reaction proceeds at its maximal velocity (Vmax). Question 26. A competitive inhibitor: A) Binds irreversibly to the enzyme’s active site. B) Decreases Vmax but not Km.
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D) NAD⁺
Answer: B Explanation: Oxaloacetate combines with acetyl-CoA to start the cycle and is regenerated at the end of each turn. Question 30. The primary electron carrier that shuttles electrons from NADH to the electron transport chain is: A) FADH₂ B) Coenzyme Q (ubiquinone) C) Cytochrome c D) NAD⁺ Answer: B Explanation: Coenzyme Q accepts electrons from NADH (Complex I) and transfers them to Complex III. Question 31. The chemiosmotic theory states that ATP synthesis is driven by: A) Direct transfer of electrons to ADP B) A proton gradient across a membrane C) Substrate-level phosphorylation only D) Light absorption by chlorophyll Answer: B Explanation: The proton motive force generated by the ETC drives ATP synthase to phosphorylate ADP. Question 32. In photosynthetic light-dependent reactions, water is split to provide electrons; the by-product is: A) Carbon dioxide B) Oxygen C) Glucose D) NADPH
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Answer: B Explanation: Photolysis of H₂O releases O₂, protons, and electrons for the photosynthetic electron transport chain. Question 33. The Calvin cycle fixes carbon using which enzyme? A) Hexokinase B) Rubisco C) ATP synthase D) Pyruvate kinase Answer: B Explanation: Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes CO₂ fixation in the Calvin cycle. Question 34. Which phase of the cell cycle is primarily dedicated to DNA replication? A) G B) S C) G D. M Answer: B Explanation: The S (synthesis) phase is when each chromosome is duplicated to form sister chromatids. Question 35. The checkpoint that ensures all chromosomes are properly attached to the spindle before anaphase is the: A) G1 checkpoint B) G2 checkpoint C) Metaphase (spindle) checkpoint D) Cytokinesis checkpoint Answer: C
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Question 39. Crossing over occurs during which meiotic stage? A) Prophase I (pachytene) B) Metaphase I C) Anaphase II D) Telophase I Answer: A Explanation: Synapsis and recombination (crossing over) happen in prophase I, specifically the pachytene substage. Question 40. Autocrine signaling is characterized by: A) Hormones traveling through the bloodstream B) A cell responding to a signal it secretes itself C) Direct contact via gap junctions D) Neurons releasing neurotransmitters across a synapse Answer: B Explanation: In autocrine signaling, the secreting cell also possesses receptors for its own ligand. Question 41. Which second messenger is most commonly associated with G-protein-coupled receptor activation? A) cAMP B) ATP C) NAD⁺ D) Glucose Answer: A Explanation: Activation of adenylate cyclase by G-proteins raises intracellular cAMP levels. Question 42. A ligand that binds to a receptor on a neighboring cell without entering the bloodstream is acting in a:
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A) Endocrine manner B) Paracrine manner C) Autocrine manner D) Juxtacrine manner Answer: B Explanation: Paracrine signals act locally, diffusing short distances to affect adjacent cells. Question 43. The intrinsic pathway of apoptosis is initiated by: A) Death-receptor ligands (e.g., FasL) B) DNA damage leading to cytochrome c release C) Extracellular cytokines D) Calcium influx through voltage-gated channels Answer: B Explanation: Internal stress (DNA damage, mitochondrial outer membrane permeabilization) releases cytochrome c, activating caspases. Question 44. Which protein family forms pores in the mitochondrial outer membrane during apoptosis? A) Bcl-2 family (pro-apoptotic members) B) Tubulin C) Actin D) Integrins Answer: A Explanation: Pro-apoptotic Bcl-2 members (e.g., Bax, Bak) oligomerize to create channels for cytochrome c release. Question 45. The term “endocytosis” most accurately describes: A) Export of vesicles from the cell B) Ingestion of extracellular material by vesicle formation
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C) Houses the flagellar motor D) Functions as the equivalent of a nucleus Answer: B Explanation: The periplasmic space lies between the inner membrane and outer membrane, containing a thin peptidoglycan layer and various enzymes. Question 49. In eukaryotic cells, the nucleoplasm is analogous to the: A) Cytosol of prokaryotes B) Mitochondrial matrix C) Extracellular matrix D) Golgi lumen Answer: A Explanation: The nucleoplasm is the gel-like interior of the nucleus, similar in composition to cytosol. Question 50. Which type of transport protein undergoes a conformational change to move a solute across the membrane? A) Channel protein B) Carrier (carrier-mediated) protein C) ATP synthase D) Glycophorin Answer: B Explanation: Carriers bind substrate on one side, change shape, and release it on the opposite side. Question 51. The primary function of the rough endoplasmic reticulum is to: A) Synthesize lipids B) Produce ribosomal RNA C) Translate membrane-bound and secretory proteins D) Generate ATP
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Answer: C Explanation: Ribosomes attached to the rough ER synthesize proteins destined for membranes, lysosomes, or secretion. Question 52. Which structural feature distinguishes a plant cell from an animal cell? A) Presence of centrioles B) Presence of a cell wall composed of cellulose C) Presence of lysosomes D) Presence of a single circular chromosome Answer: B Explanation: Plant cells have a rigid cellulose cell wall; animal cells do not. Question 53. The mitochondrial DNA (mtDNA) is inherited: A) Paternally B) Maternal only C) Equally from both parents D) Randomly from either parent Answer: B Explanation: mtDNA is transmitted through the oocyte cytoplasm, leading to maternal inheritance. Question 54. Which of the following statements about intermediate filaments is correct? A) They are composed of actin subunits. B) They provide tensile strength and are not dynamic like microtubules. C) They form the mitotic spindle. D) They are the primary site of ATP generation. Answer: B
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Question 58. Which of the following is a characteristic of a hyperpolarizing ion channel? A) Allows Na⁺ influx, depolarizing the membrane. B) Permits K⁺ efflux, making the interior more negative. C. Allows Cl⁻ influx, neutralizing charge. D. Allows Ca²⁺ influx, triggering action potentials. Answer: B Explanation: Opening K⁺ channels lets positive charge leave the cell, increasing negativity (hyperpolarization). Question 59. In the context of enzyme kinetics, the Michaelis constant (Km) reflects: A) The maximum velocity (Vmax) of the reaction. B) The substrate concentration at which the reaction rate is half of Vmax. C. The inhibitor concentration needed to halve activity. D. The amount of enzyme required for full activity. Answer: B Explanation: Km is the substrate concentration at which the reaction proceeds at ½ Vmax, indicating enzyme affinity. Question 60. Which of the following best describes the role of NAD⁺ in glycolysis? A) It donates a phosphate group to ADP. B) It accepts electrons, becoming NADH. C. It acts as a substrate for hexokinase. D. It transports pyruvate into mitochondria. Answer: B Explanation: NAD⁺ is reduced to NADH when glyceraldehyde- 3 - phosphate is oxidized, capturing electrons.
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Question 61. The enzyme that catalyzes the conversion of phosphoenolpyruvate to pyruvate, generating ATP, is: A) Hexokinase B) Pyruvate kinase C) Phosphofructokinase- D) Lactate dehydrogenase Answer: B Explanation: Pyruvate kinase performs substrate-level phosphorylation in the final step of glycolysis. Question 62. During oxidative phosphorylation, the proton gradient is established across which membrane? A) Outer mitochondrial membrane B) Inner mitochondrial membrane C) Plasma membrane D) Thylakoid membrane Answer: B Explanation: The inner mitochondrial membrane houses the ETC and pumps protons into the intermembrane space, creating the gradient. Question 63. Which molecule serves as the final electron acceptor in aerobic respiration? A) NAD⁺ B) FAD C) O₂ D) CO₂ Answer: C Explanation: Molecular oxygen accepts electrons at Complex IV, forming water. Question 64. In the Calvin cycle, the molecule that accepts CO₂ to form a six-carbon intermediate is:
