Q60. In which of the following processes is active transport NOT used?
[UPSC CDS (II), General Knowledge 2026]
(a) Reabsorption of amino acids and glucose from kidney into blood
(b) Loading sugar from photosynthesizing leaf cells into phloem tissue for transportation
(c) Passage of Na⁺ and Cl⁻ through hydrophilic channels formed by protein molecules
(d) Absorption of glucose and electrolytes into the bloodstream
Answer: (c) Passage of Na⁺ and Cl⁻ through hydrophilic channels formed by protein molecules
Explanation: Ion passage through an open channel can occur by facilitated diffusion, following the electrochemical gradient without direct ATP consumption. By contrast, active transport moves substances against a gradient and needs energy, either directly or through coupling to another gradient.
Q59. Which one of the following is NOT true of mitotic cell division?
[UPSC CDS (II), General Knowledge 2026]
(a) The two daughter nuclei have the same number of chromosomes
(b) Mitosis enables replacement of cells and tissue repair
(c) Asexual reproduction in eukaryotes can occur through mitosis
(d) Cells become haploid as a result of mitosis
Answer: (d) Cells become haploid as a result of mitosis
Explanation: Mitosis ordinarily maintains the chromosome number of the parent cell, generating genetically similar daughter nuclei. Haploid cells arise through reduction division in meiosis instead. Mitosis supports growth, tissue repair and several forms of asexual reproduction in eukaryotes.
Q58. Which one of the following is NOT found in a prokaryotic cell?
[UPSC CDS (II), General Knowledge 2026]
(a) Cell wall
(b) Ribosome
(c) Nuclear membrane
(d) Plasmid DNA
Answer: (c) Nuclear membrane
Explanation: Prokaryotes lack a membrane-enclosed nucleus. Their principal chromosome occupies a nucleoid region, and extra circular DNA may occur as plasmids. They possess ribosomes for protein synthesis; many also have a cell wall, although some groups lack one.
Q57. Which material did Robert Hooke use to first discover “cells”?
[RRB Group D, 19 August 2026, Shift 2]
(a) Cork slice
(b) Human cheek
(c) Onion peel
(d) Leaf surface
Answer: (a) Cork slice
Explanation: Robert Hooke examined thin slices of cork using a microscope in 1665. He observed tiny boxlike compartments and named them cells. The compartments were dead plant cell walls; the discovery was later described in his influential book Micrographia.
Q56. Identify the correctly matched cell–structure pair.
[RRB Group D, 19 August 2026, Shift 3]
(a) Eukaryotic cell — membrane-bound endoplasmic reticulum
(b) Prokaryotic cell — mitochondria
(c) Animal cell — cell wall
(d) Bacterial cell — well-defined nucleus
Answer: (a) Eukaryotic cell — membrane-bound endoplasmic reticulum
Explanation: Eukaryotic cells possess internal membrane-bound organelles including the endoplasmic reticulum. Prokaryotes lack mitochondria and a true nucleus. Most animal cells lack cell walls; bacteria generally contain a cell wall but their chromosomal DNA lies in a nucleoid.
Q55. Which organelle is physically continuous with the nuclear envelope?
[RRB Group D, 20 August 2026, Shift 1]
(a) Endoplasmic reticulum
(b) Mitochondria
(c) Golgi body
(d) Lysosome
Answer: (a) Endoplasmic reticulum
Explanation: The outer nuclear membrane continues into the membrane of the endoplasmic reticulum, and the perinuclear space joins its lumen. This continuity connects nuclear organization with cellular production and processing of proteins and lipids, although other organelles remain separate structures.
Q54. The central cytoplasmic region of a prokaryotic cell containing nucleic acids is called:
[UPSC CDS (I), General Knowledge 2026]
(a) Nucleus
(b) Nucleoid
(c) Nucleolus
(d) Plastid
Answer: (b) Nucleoid
Explanation: The nucleoid is the DNA-containing area of bacterial and archaeal cells, without a surrounding nuclear envelope. Unlike the true nucleus of a eukaryotic cell, it is not membrane bound. The nucleolus is a subnuclear region associated with ribosome production.
Q53. The antibiotic penicillin can kill invading bacteria without harming human cells because it targets the bacterial:
[UPSC CDS (I), General Knowledge 2026]
(a) Cell wall
(b) Plasma membrane
(c) Ribosome
(d) Chromosome
Answer: (a) Cell wall
Explanation: Penicillin inhibits enzymes involved in cross-linking peptidoglycan, a vital component of many bacterial cell walls. Human cells have plasma membranes but no peptidoglycan walls. This difference explains penicillin’s selective action, especially against susceptible actively growing bacteria.
Q52. In which cell type is the highest number of lysosomes likely to occur?
[UPSC CDS (I), General Knowledge 2026]
(a) Pancreatic cell
(b) Ovarian cell
(c) Thigh muscle cell of a runner
(d) White blood cell
Answer: (d) White blood cell
Explanation: Phagocytic white blood cells ingest microorganisms and cellular debris, then fuse phagosomes with enzyme-containing lysosomes for destruction. Their intensive digestive activity explains their abundant lysosomal machinery. Muscle cells, by comparison, often have numerous mitochondria to meet energy demand.
Q51. A cell is damaged and its lysosomes burst, releasing digestive enzymes into the cytoplasm. What is most likely to happen?
[RRB Group D, 30 December 2025, Shift 2]
(a) The mitochondria produce more energy
(b) The cell grows in size
(c) The cell destroys itself and dies
(d) The nucleus divides rapidly
Answer: (c) The cell destroys itself and dies
Explanation: Lysosomes carry acid hydrolases that digest biological macromolecules. Severe lysosomal rupture can contribute to cellular self-digestion and injury. The term suicidal bags refers to this destructive potential, although ordinary programmed cell death involves more elaborate regulatory pathways.
Q50. Which of the following cell organelles does NOT have its own DNA?
[RRB Group D, 14 December 2025, Shift 2]
(a) Nucleus
(b) Plastids
(c) Mitochondria
(d) Lysosomes
Answer: (d) Lysosomes
Explanation: Lysosomes are membrane-bound digestive compartments containing hydrolytic enzymes but no independent genome. Mitochondria and plastids retain small DNA molecules and limited protein-synthesis machinery. The nucleus holds most of a eukaryotic cell’s DNA, organized into chromosomes.
Q49. Which cell organelle contains digestive enzymes and keeps the cell clean by digesting foreign material and worn-out organelles?
[RRB Group D, 12 December 2025, Shift 2]
(a) Chloroplast
(b) Ribosome
(c) Lysosome
(d) Chromoplast
Answer: (c) Lysosome
Explanation: Lysosomes contain digestive hydrolases, operating in an acidic interior. They break down engulfed microbes and recycle damaged components through intracellular digestion and autophagy. Chloroplasts support photosynthesis, whereas ribosomes assemble proteins and chromoplasts store pigment in certain plant tissues.
Q48. What is the role of lysosomes in a cell?
[RRB Group D, 1 December 2025, Shift 1]
(a) To store proteins
(b) To produce ATP
(c) To transport products
(d) To digest foreign material
Answer: (d) To digest foreign material
Explanation: Lysosomal enzymes degrade foreign particles, waste and cellular material inside membrane-enclosed compartments. Their contents include proteases, lipases and nucleases. Cellular ATP is principally generated through respiration, while trafficking and storage involve other structures, so digestion is the defining choice.
Q47. Select the incorrect statement regarding mitochondria.
[RPSC Senior Teacher Grade II (Science), Paper II, 9 September 2025]
(a) The mitochondrial matrix contains circular DNA
(b) Inner and outer mitochondrial membranes have different enzyme complements
(c) The inner membrane forms folds called cristae
(d) The mitochondrial matrix possesses 80S ribosomes
Answer: (d) The mitochondrial matrix possesses 80S ribosomes
Explanation: Mitochondria have their own translation machinery. In school-level classifications, their ribosomes are described as prokaryote-like, rather than the 80S ribosomes typical of eukaryotic cytoplasm. Cristae increase inner-membrane surface area, while mitochondrial DNA is present in the matrix.
Q46. Which one of the following organelles can be seen in a prokaryotic cell?
[UPSC CDS (II), General Knowledge 2025]
(a) Mitochondria
(b) Definitive nucleus
(c) Ribosomes
(d) Golgi bodies
Answer: (c) Ribosomes
Explanation: Both prokaryotes and eukaryotes require ribosomes to translate messenger RNA into proteins. Typical bacteria have 70S ribosomes and lack a membrane-bound nucleus, mitochondria and Golgi bodies. Ribosomes are therefore an important exception to the absence of complex organelles.
Q45. Why does the rough endoplasmic reticulum appear rough under a microscope?
[UPSC CDS (I), General Knowledge 2025]
(a) Ribosomes are present on its surface
(b) Ribosomes are absent from its surface
(c) Lysosomes are present on its surface
(d) Mitochondria are present on its surface
Answer: (a) Ribosomes are present on its surface
Explanation: Attached ribosomes create the granular appearance of rough endoplasmic reticulum. These ribosomes synthesize proteins destined for secretion, membranes or certain organelles. Smooth endoplasmic reticulum lacks surface ribosomes and contributes to lipid synthesis and detoxification.
Q44. What is the structural and functional unit of life?
[70th BPSC Preliminary Examination, 13 December 2024]
(a) Cell
(b) Organ
(c) Tissue
(d) Organism
Answer: (a) Cell
Explanation: The cell is the smallest structural unit that carries out the essential processes of life. In multicellular organisms, related cells build tissues, tissues form organs and organs form systems. Unicellular organisms perform all life functions within one cell.
Q43. Which of the following statements is NOT true?
[UPPSC PCS Preliminary Examination 2024, GS Paper I]
(a) The nucleus does not play a role in cellular reproduction
(b) Chromosomes carry hereditary information
(c) Chromosomes consist of DNA and proteins
(d) A functional segment of DNA is called a gene
Answer: (a) The nucleus does not play a role in cellular reproduction
Explanation: The nucleus is crucial for reproduction of eukaryotic cells because its chromosomes replicate and are distributed during cell division. Chromosomes consist of DNA associated with proteins, and genes are functional DNA sequences involved in the expression of inherited traits.
Q42. Match the cell structures with their functions:
(i) Cell membrane,
(ii) Smooth ER,
(iii) Golgi apparatus,
(iv) Ribosomes;
(a) Protein synthesis,
(b) Glycolipids/glycoproteins formation,
(c) Lipid synthesis,
(d) Molecular transport.
[SSC MTS, 5 November 2024, Shift 3]
(a) i–d, ii–c, iii–b, iv–a
(b) i–c, ii–d, iii–b, iv–a
(c) i–a, ii–c, iii–d, iv–b
(d) i–c, ii–d, iii–a, iv–b
Answer: (a) i–d, ii–c, iii–b, iv–a
Explanation: The plasma membrane regulates molecular entry and exit. Smooth ER synthesizes many lipids; the Golgi apparatus modifies and processes glycoproteins and glycolipids; ribosomes translate RNA into proteins. Matching these specialized roles yields i–d, ii–c, iii–b and iv–a.
Q41. Who first postulated that cells are generated from pre-existing cells?
[SSC MTS, 17 October 2024, Shift 1]
(a) Jennifer Doudna
(b) Rudolf Virchow
(c) William Harvey
(d) Carl Linnaeus
Answer: (b) Rudolf Virchow
Explanation: Rudolf Virchow popularized the principle Omnis cellula e cellula, meaning every cell arises from an existing cell. This extended earlier cell-theory work by Schleiden and Schwann and rejected the idea that new living cells appear spontaneously from nonliving matter.
Q40. Which of the following possesses the largest isolated single cell?
[SSC MTS, 14 November 2024, Shift 2]
(a) Ostrich egg
(b) Human brain
(c) Amoeba
(d) Blue whale
Answer: (a) Ostrich egg
Explanation: The ostrich ovum is generally cited in school biology as the largest single cell visible without a microscope. A brain and a whale are multicellular organisms or structures, whereas an amoeba is a microscopic unicellular organism.
Q39. Which organelle in animal cells can digest foreign materials?
[UPSC CDS (II), General Knowledge 2024]
(a) Endoplasmic reticulum
(b) Lysosome
(c) Golgi body
(d) Mitochondria
Answer: (b) Lysosome
Explanation: Lysosomes receive foreign particles after uptake and digest them with hydrolytic enzymes. They also help recycle aged cellular components. The Golgi apparatus processes and sorts materials; mitochondria generate ATP; and endoplasmic reticulum participates in protein and lipid metabolism.
Q38. Which of the following causes enlargement and extension growth of plant cells?
[SSC CHSL Tier I, 8 July 2024, Shift 1]
(a) Turgor pressure
(b) Imbibition
(c) Pressure potential
(d) Osmotic pressure
Answer: (a) Turgor pressure
Explanation: As water enters a plant cell, the expanding vacuole raises turgor pressure against the cell wall. When the wall can loosen and extend, this pressure drives cell enlargement. Turgor also supports herbaceous tissues and reduces wilting.
Q37. In which year did Rudolf Virchow formulate the aphorism “Omnis cellula e cellula”?
[SSC CHSL Tier I, 17 August 2023, Shift 4]
(a) 1855
(b) 1869
(c) 1840
(d) 1835
Answer: (a) 1855
Explanation: In 1855, Rudolf Virchow advanced the concept that cells arise from pre-existing cells. This concept became a major principle of cell theory and clarified continuity between generations of cells through cell division instead of spontaneous formation.
Q36. Which cell organelle is known as the cell’s post office?
[SSC CHSL Tier I, 14 August 2023, Shift 1]
(a) Nucleus
(b) Golgi apparatus
(c) Ribosome
(d) Plastid
Answer: (b) Golgi apparatus
Explanation: The Golgi apparatus modifies, sorts and packages proteins and lipids into transport vesicles. Because it directs cellular products to their destinations, it is compared to a post office. Its stacks of flattened membrane sacs are called cisternae.
Q35. Which part of a cell converts nutrients into energy?
[SSC CHSL Tier I, 3 August 2023, Shift 2]
(a) Cell membrane
(b) Lysosomes
(c) Mitochondria
(d) Chromosome
Answer: (c) Mitochondria
Explanation: Mitochondria convert energy released by nutrient oxidation into ATP during aerobic respiration. The Krebs cycle occurs in the matrix, and the electron-transport system functions in the inner membrane. This energy-producing role explains the expression powerhouse of the cell.
Q34. Which is the primary structural component responsible for most mechanical strength of a plant cell wall?
[SSC MTS, 8 September 2023, Shift 1]
(a) Heparin
(b) Glycogen
(c) Chitin
(d) Cellulose
Answer: (d) Cellulose
Explanation: Cellulose chains aggregate into strong microfibrils that provide tensile strength to plant cell walls. Hemicelluloses and pectins contribute to the surrounding matrix. Chitin instead reinforces fungal walls, while glycogen serves mainly as an energy-storage polysaccharide.
Q33. In which year did Robert Hooke introduce the term “cell”?
[SSC MTS, 1 September 2023, Shift 2]
(a) 1875
(b) 1675
(c) 1665
(d) 1765
Answer: (c) 1665
Explanation: Hooke used the word cell in 1665 after observing cork tissue. Its small compartments reminded him of little rooms. He presented the observation in Micrographia, establishing an important historical starting point for the microscopic study of living structures.
Q32. Cell wall is absent in which one of the following organisms?
[UPSC CDS (II), General Knowledge 2023]
(a) Bacteria
(b) Diatom
(c) Mushroom
(d) Tapeworm
Answer: (d) Tapeworm
Explanation: Tapeworms are animals, and animal cells do not have rigid walls outside their plasma membranes. Bacteria generally possess peptidoglycan walls, mushrooms have fungal walls rich in chitin, and diatoms have silica-rich protective coverings called frustules.
Q31. If human red blood cells are placed in normal saline isotonic to blood, what happens?
[UPSC CDS (I), General Knowledge 2023]
(a) They swell
(b) They swell and burst
(c) They shrink
(d) Their diameter remains unchanged
Answer: (d) Their diameter remains unchanged
Explanation: An isotonic medium has approximately the same effective osmotic concentration as the red-cell interior. Water continues to cross the membrane in both directions, but there is no net movement. The cells therefore retain their normal size.
Q30. Which cell component contains the hereditary material, DNA?
[SSC MTS (2022 cycle), 3 May 2023, Shift 1]
(a) Cell wall
(b) Nucleus
(c) Cell membrane
(d) Cytoplasm
Answer: (b) Nucleus
Explanation: In eukaryotic cells, most hereditary DNA is enclosed within the nucleus and arranged into chromosomes. The nuclear envelope separates it from the cytoplasm. Mitochondria also contain a small DNA genome, but the nucleus houses the majority of genetic material.
Q29. Match the organelles and functions:
(i) Mitochondria,
(ii) Ribosomes,
(iii) Nucleus,
(iv) Lysosomes;
(a) Protein synthesis,
(b) Cell regulation,
(c) Intracellular digestion,
(d) Energy generation.
[SSC CGL Tier I, 5 December 2022, Shift 3]
(a) i–c, ii–a, iii–d, iv–b
(b) i–b, ii–a, iii–c, iv–d
(c) i–a, ii–b, iii–c, iv–d
(d) i–d, ii–a, iii–b, iv–c
Answer: (d) i–d, ii–a, iii–b, iv–c
Explanation: Mitochondria produce much of the cell’s ATP, ribosomes build proteins, the nucleus regulates gene expression and cell functions, and lysosomes digest cellular material. This gives the correspondence i–d, ii–a, iii–b and iv–c.
Q28. Identify the option that does NOT represent a prokaryotic cell.
[SSC CGL Tier I, 3 December 2022, Shift 3]
(a) Mycoplasma
(b) Blue-green alga
(c) Sperm
(d) Pleuropneumonia-like organism
Answer: (c) Sperm
Explanation: Sperm is a specialized animal reproductive cell and is eukaryotic. Mycoplasma and pleuropneumonia-like organisms are bacteria; blue-green algae are cyanobacteria. Prokaryotes lack a membrane-enclosed nucleus, while sperm carry chromosomes in a true nucleus.
Q27. What happens when an animal cell is surrounded by a medium having a lower concentration of water?
[UPSC NDA (II), General Ability Test, 4 September 2022]
(a) The cell loses water
(b) There is no net water movement
(c) The cell gains water
(d) The cell swells
Answer: (a) The cell loses water
Explanation: Water moves by osmosis across the plasma membrane from higher water potential toward lower water potential. A concentrated external medium draws water out of an animal cell, causing shrinkage. A dilute external medium would instead tend to produce swelling.
Q26. A cell cannot synthesize lipids. Which organelle may be defective?
[UPSC NDA (I), General Ability Test, 10 April 2022]
(a) Smooth endoplasmic reticulum
(b) Golgi bodies
(c) Lysosomes
(d) Mitochondria
Answer: (a) Smooth endoplasmic reticulum
Explanation: Smooth endoplasmic reticulum is a major location for synthesis of phospholipids, cholesterol and other lipids. It also contributes to detoxification and calcium handling in specialized cells. Ribosome-studded rough ER is more directly involved in protein synthesis.
Q25. Which statements about the breakdown of glucose are true?
(i) In cytoplasm, glucose breaks down into four-carbon pyruvate.
(ii) Without oxygen, pyruvate may form lactic acid.
(iii) Without oxygen, pyruvate may form carbon dioxide and ethanol.
[CGPSC State Service Preliminary Examination (2021 cycle), 13 February 2022]
(a) (i), (ii) and (iii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) Only (iii)
Answer: (c) (ii) and (iii)
Explanation: Glycolysis occurs in cytoplasm and yields three-carbon pyruvate, making statement (i) incorrect. Without oxygen, muscle cells can produce lactic acid, while yeast ferments pyruvate into ethanol and carbon dioxide. Thus both statements (ii) and (iii) are correct.
Q24. The study of cells is called ________.
[RRB NTPC CBT I, 8 February 2021, Shift 2]
(a) Serology
(b) Etiology
(c) Cytology
(d) Cytoplasm
Answer: (c) Cytology
Explanation: Cytology is the scientific study of cells, including their structure, activity and abnormalities. Modern cell biology also examines molecular mechanisms within cells. Serology concerns serum-related investigations, etiology concerns causes, and cytoplasm is cellular material rather than a field of study.
Q23. Which organelle keeps the cell clean by digesting foreign material and worn-out organelles?
[RRB NTPC CBT I, 26 July 2021, Shift 1]
(a) Mitochondria
(b) Endoplasmic reticulum
(c) Golgi apparatus
(d) Lysosome
Answer: (d) Lysosome
Explanation: Lysosomes fuse with compartments containing unwanted material and break the contents down using digestive enzymes. This disposal and recycling function maintains cellular health. The Golgi apparatus helps generate lysosomes but is primarily concerned with modification, sorting and packaging.
Q22. The smallest unit of life capable of independent existence is:
[RRB NTPC CBT I, 7 January 2021, Shift 2]
(a) Protoplasm
(b) Cytoplasm
(c) Cell
(d) Vacuoles
Answer: (c) Cell
Explanation: An individual cell can carry out fundamental processes such as metabolism, responsiveness and reproduction. Cytoplasm and vacuoles are components of a cell rather than independent living units. Unicellular organisms demonstrate how one complete cell can function as an organism.
Q21. Osmosis is the movement of water molecules from:
[UPSC CDS (I), General Knowledge 2021]
(a) Higher to lower water concentration through a cell wall
(b) Lower to higher water concentration through a fully permeable membrane
(c) Higher to lower water concentration through a fully permeable membrane
(d) Higher to lower water concentration through a semipermeable membrane
Answer: (d) Higher to lower water concentration through a semipermeable membrane
Explanation: Osmosis is passive movement of water across a selectively permeable membrane from higher water potential to lower water potential. Unlike a freely permeable wall, such a membrane restricts some solutes. The process explains cell swelling, shrinkage and plant turgor.
Q20. Which statements correctly describe differences between plant and animal cells?
1. Plant cells have cellulose walls, animal cells do not.
2. Plant cells lack plasma membranes.
3. Mature plant cells generally have one large vacuole, animal cells may have small vacuoles.
[UPSC Civil Services Preliminary Examination 2020]
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c) 1 and 3 only
Explanation: Plant cells possess both a cellulose-rich cell wall and an underlying plasma membrane. Their large central vacuole commonly maintains turgor. Animal cells lack cellulose walls and may have small vacuoles. Therefore statements one and three are correct, but two is false.
Q19. Which is the energy currency for cellular processes?
[UPSC CDS (I), General Knowledge 2020]
(a) Glucose
(b) ATP
(c) ADP
(d) Pyruvic acid
Answer: (b) ATP
Explanation: ATP stores readily transferable energy in phosphoanhydride bonds and couples energy-releasing reactions to cellular work. Hydrolysis to ADP and inorganic phosphate powers many biological processes. Glucose is a metabolic fuel, whereas ATP is the immediate energy-transfer molecule.
Q18. Which one of the following best defines active transport?
[UPSC CDS (II), General Knowledge 2019]
(a) Movement against a diffusion gradient using energy from respiration
(b) Movement against a diffusion gradient without energy
(c) Movement against a diffusion gradient using energy from photosynthesis only
(d) Movement along a diffusion gradient using energy from respiration
Answer: (a) Movement against a diffusion gradient using energy from respiration
Explanation: Active transport moves substances against their concentration or electrochemical gradients and therefore requires energy. ATP made during cellular respiration commonly powers membrane transporters either directly or indirectly. Simple diffusion and facilitated diffusion ordinarily proceed down a gradient.
Q17. In photosynthetic prokaryotic bacteria, chlorophyll is associated with:
[UPSC CDS (II), General Knowledge 2019]
(a) Plastids
(b) Membranous vesicles
(c) Nucleoids
(d) Chromosomes
Answer: (b) Membranous vesicles
Explanation: Photosynthetic bacteria do not possess the membrane-bound chloroplasts of plants. Their photosynthetic pigments occur in internal or specialized membranes. These membranes carry the systems that capture light energy; the nucleoid instead stores chromosomal DNA and does not act as a chloroplast.
Q16. Which function is NOT carried out by smooth endoplasmic reticulum?
[UPSC CDS (I), General Knowledge 2019]
(a) Transport of materials
(b) Synthesis of lipids
(c) Synthesis of proteins
(d) Synthesis of steroid hormones
Answer: (c) Synthesis of proteins
Explanation: Smooth ER contributes to lipid and steroid synthesis and other metabolic tasks. Because it lacks attached ribosomes, it is not the main site of protein translation. Proteins intended for secretion are commonly made by ribosomes on rough endoplasmic reticulum.
Q15. Which organelle is NOT found in prokaryotic cells?
[UPSC NDA (I), General Ability Test, 22 April 2018]
(a) Cell wall
(b) Mitochondria
(c) Plasma membrane
(d) Ribosome
Answer: (b) Mitochondria
Explanation: Prokaryotes such as bacteria have plasma membranes, cytoplasmic ribosomes and often cell walls. They do not possess membrane-bound mitochondria. Cellular respiration can occur through their cytoplasmic membrane and associated enzyme systems instead of a separate mitochondrial organelle.
Q14. The cell walls of many fungi are composed of which tough complex sugar?
[SSC CHSL, 14 March 2018, Shift 2]
(a) Pectin
(b) Suberin
(c) Cellulose
(d) Chitin
Answer: (d) Chitin
Explanation: Chitin is a strong nitrogen-containing polysaccharide that reinforces fungal cell walls. Plant walls are primarily cellulose-based, whereas pectin forms part of their wall matrix. Chitin also appears in arthropod exoskeletons and gives mechanical strength to biological structures.
Q13. Which of the following is NOT a feature found in almost every cell?
[SSC CHSL, 16 March 2018, Shift 2]
(a) Cell wall
(b) Plasma membrane
(c) Nucleus
(d) Cytoplasm
Answer: (a) Cell wall
Explanation: Cell walls occur in plants, fungi and many prokaryotes but are absent from animal cells. A plasma membrane and cytoplasm are basic cellular features. The nucleus is not universal either, because prokaryotes lack one; the intended contrast here concerns walls.
Q12. Which process does NOT occur inside mitochondria?
[RPSC Senior Teacher Grade II (Science), 1 November 2018]
(a) Krebs cycle
(b) Glycolysis
(c) ATP synthesis
(d) Electron transport chain
Answer: (b) Glycolysis
Explanation: Glycolysis occurs in the cytosol, where glucose is converted to pyruvate. The mitochondrial matrix supports the Krebs cycle, while the inner membrane contains the electron-transport system and ATP synthase. Mitochondria therefore perform later stages of aerobic respiration.
Q11. Which among the following does not have a cell wall?
[SSC CGL Tier I, 11 August 2017, Shift 3]
(a) Euglena
(b) Paramecium
(c) Gonyaulax
(d) Mycoplasma
Answer: (d) Mycoplasma
Explanation: The official key identifies Mycoplasma, a bacterium without a peptidoglycan wall. However, the wording is scientifically ambiguous: Euglena and Paramecium also lack conventional cell walls. The keyed response should therefore be understood as the examination answer, not a unique biological distinction.
Q10. Which organelles are involved in protein transport?
[RPSC Senior Teacher Grade II (Science), 1 July 2017]
(a) Endoplasmic reticulum and Golgi bodies
(b) Golgi bodies and mitochondria
(c) Endoplasmic reticulum and mitochondria
(d) Lysosomes, Golgi bodies and nucleolus
Answer: (a) Endoplasmic reticulum and Golgi bodies
Explanation: Proteins destined for secretion commonly enter rough endoplasmic reticulum, then travel in vesicles to the Golgi apparatus. The Golgi modifies, sorts and repackages them for delivery. These structures form major components of the eukaryotic endomembrane trafficking system.
Q9. Peptide synthesis inside a cell usually occurs in:
[UPPSC GIC Lecturer (Botany) Examination 2017]
(a) Mitochondria
(b) Chromoplasts
(c) Ribosomes
(d) Golgi bodies
Answer: (c) Ribosomes
Explanation: Ribosomes join amino acids into polypeptide chains using the codon sequence of messenger RNA. This process is translation. Ribosomes occur freely in cytoplasm or attach to rough ER; mitochondria synthesize some proteins on their own ribosomes too.
Q8. Which cells do not contain a nucleus? 1. Root hair cells 2. Red blood cells 3. Platelets 4. Monocytes
[UPSC CDS (II), General Knowledge, 23 October 2016]
(a) 1 only
(b) 2 and 3 only
(c) 1, 2 and 4
(d) 2, 3 and 4
Answer: (b) 2 and 3 only
Explanation: Mature mammalian red blood cells expel their nuclei, and platelets are anucleate cell fragments involved in clotting. Root hair cells and monocytes possess nuclei. Lack of a nucleus helps mammalian erythrocytes accommodate more haemoglobin but limits their capacity for division.
Q7. The living content of the cell is called protoplasm. It is composed of:
[UPSC CDS (I), General Knowledge, 14 February 2016]
(a) Cytoplasm only
(b) Cytoplasm and nucleoplasm
(c) Nucleoplasm only
(d) Cytoplasm, nucleoplasm and other organelles
Answer: (d) Cytoplasm, nucleoplasm and other organelles
Explanation: Protoplasm is a traditional collective term for a cell’s living contents, including cytoplasm, nucleoplasm and organelles. Cytoplasm excludes the contents of the nucleus, whereas nucleoplasm is inside it. The question tests the broader meaning of protoplasm.
Q6. Which organelle helps in the formation of the sperm acrosome?
[RPSC Senior Teacher Grade II (Science) Examination 2015]
(a) Mitochondria
(b) Golgi complex
(c) Ribosomes
(d) Chloroplast
Answer: (b) Golgi complex
Explanation: The sperm acrosome develops from the Golgi apparatus during sperm formation. It contains enzymes used during penetration of protective layers around the ovum. The Golgi’s role in processing and packaging biological products makes this specialized structure possible.
Q5. Which is the longest cell in animals?
[WBCS Preliminary Examination 2014]
(a) Nerve cell
(b) Hepatocyte
(c) Blood cell
(d) Muscle cell
Answer: (a) Nerve cell
Explanation: A neuron can extend over a considerable distance through its axon, making nerve cells the longest cells in many animals. Certain human motor neurons run from the spinal cord to the feet, carrying electrical signals across long distances.
Q4. Which part of the animal cell is called its powerhouse?
[MPPSC Preliminary Examination 2010]
(a) Cell wall
(b) Nucleus
(c) Mitochondria
(d) Entire cell
Answer: (c) Mitochondria
Explanation: Mitochondria are described as the powerhouse because their inner membranes generate much of the cell’s ATP through oxidative phosphorylation. Glycolysis starts in the cytoplasm, after which aerobic metabolism continues in mitochondria. They also possess their own DNA.
Q3. The plasma membrane is mainly built up of:
[UPPCS Main Examination 2008]
(a) Protein
(b) Lipid
(c) Carbohydrate
(d) Both protein and lipid
Answer: (d) Both protein and lipid
Explanation: Biological membranes consist chiefly of a lipid bilayer containing integral and peripheral proteins. Lipids form the permeability barrier; proteins act as channels, transporters, receptors and enzymes. Carbohydrate chains can occur on the outer surface but are not the primary framework.
Q2. Which of the following becomes zero in a fully turgid plant cell?
[WBCS Preliminary Examination 2003]
(a) Water potential
(b) Wall pressure
(c) Osmotic pressure
(d) All of the above
Answer: (a) Water potential
Explanation: In a fully turgid cell at equilibrium with pure water, the positive pressure potential balances the negative solute potential, making total water potential zero under the usual reference convention. Neither osmotic pressure nor wall pressure is necessarily zero.
Q1. Which one of the following statements is correct?
[UPSC Civil Services Preliminary Examination 2002]
(a) Prions are the smallest free-living cells
(b) Mycoplasma cell walls consist of amino sugars
(c) Viroids consist of single-stranded RNA molecules
(d) Rickettsiae lack cell walls
Answer: (c) Viroids consist of single-stranded RNA molecules
Explanation: Viroids are tiny infectious circular single-stranded RNA molecules, especially associated with plant disease. They lack a protein coat. Prions are infectious proteins rather than living cells; mycoplasmas lack cell walls; and rickettsiae are bacteria that possess a cell envelope.