Chapter 8: Cell: The Unit of Life – MCQs
🔬 Cell: The Unit of Life – MCQs
Part 1 (Q1–Q25)
Q1. The cell is the basic unit of
A) DNA
B) Life ✅
C) Nucleus
D) Protein
Explanation: Cell is the structural, functional, and genetic unit of life (Cell Theory).
Q2. The term “cell” was first used by
A) Robert Hooke ✅
B) Schleiden
C) Schwann
D) Virchow
Explanation: Robert Hooke (1665) observed cork cells under a microscope and coined the term “cell.”
Q3. Cell theory was proposed by
A) Hooke and Brown
B) Schleiden and Schwann ✅
C) Watson and Crick
D) Virchow and Darwin
Explanation: Schleiden (plants) & Schwann (animals) proposed Cell Theory in 1838–39.
Q4. “Omnis cellula e cellula” was stated by
A) Robert Hooke
B) Schleiden
C) Schwann
D) Rudolf Virchow ✅
Explanation: Virchow (1855) modified cell theory by adding that cells arise from pre-existing cells.
Q5. Prokaryotic cells lack
A) DNA
B) Nucleus ✅
C) Plasma membrane
D) Cytoplasm
Explanation: Prokaryotes (bacteria) lack a true nucleus and membrane-bound organelles.
Q6. Which is the largest cell?
A) Nerve cell
B) Ostrich egg ✅
C) Human ovum
D) Amoeba
Explanation: The ostrich egg is the largest single cell.
Q7. Which is the smallest cell?
A) Mycoplasma ✅
B) Virus
C) Bacteria
D) Fungi
Explanation: Mycoplasma is the smallest living cell (0.1–0.3 µm), smaller than bacteria.
Q8. The largest human cell is
A) Nerve cell
B) Ovum ✅
C) Muscle cell
D) RBC
Explanation: Human ovum is the largest human cell (about 100 µm).
Q9. The longest human cell is
A) RBC
B) Muscle cell
C) Nerve cell ✅
D) Epithelial cell
Explanation: Nerve cells may extend up to 1 meter in length.
Q10. Which organelle is known as the “powerhouse of cell”?
A) Nucleus
B) Ribosome
C) Mitochondria ✅
D) Golgi apparatus
Explanation: Mitochondria produce ATP, hence “powerhouse of the cell.”
Q11. Chloroplasts are found in
A) Animal cells
B) Plant cells ✅
C) Bacteria
D) Viruses
Explanation: Chloroplasts are present only in plant cells and some protists.
Q12. The site of protein synthesis is
A) Golgi bodies
B) Ribosomes ✅
C) Lysosomes
D) Nucleus
Explanation: Ribosomes (80S in eukaryotes, 70S in prokaryotes) are the sites of protein synthesis.
Q13. The “suicidal bags of cell” are
A) Peroxisomes
B) Lysosomes ✅
C) Ribosomes
D) Vacuoles
Explanation: Lysosomes contain digestive enzymes which can digest cell organelles.
Q14. Plant cell wall is made up of
A) Peptidoglycan
B) Cellulose ✅
C) Chitin
D) Glycogen
Explanation: Plant cell walls are made of cellulose, while bacterial walls are made of peptidoglycan.
Q15. The fluid mosaic model was proposed by
A) Singer and Nicolson ✅
B) Watson and Crick
C) Schleiden and Schwann
D) Robertson
Explanation: Singer and Nicolson (1972) proposed the Fluid Mosaic Model of plasma membrane.
Q16. Which organelle is involved in packaging and secretion?
A) Golgi apparatus ✅
B) Ribosome
C) Lysosome
D) Nucleus
Explanation: Golgi apparatus modifies, stores, and packages proteins & lipids.
Q17. Which organelle contains its own DNA and ribosomes?
A) Golgi apparatus
B) Lysosome
C) Mitochondria ✅
D) ER
Explanation: Mitochondria and chloroplasts have their own DNA & ribosomes, hence semi-autonomous.
Q18. The semi-fluid substance inside the cell is
A) Nucleus
B) Protoplasm
C) Cytoplasm ✅
D) Matrix
Explanation: Cytoplasm is the semi-fluid matrix where organelles are embedded.
Q19. The organelle responsible for photosynthesis is
A) Mitochondria
B) Ribosomes
C) Chloroplast ✅
D) Golgi apparatus
Explanation: Chloroplasts contain chlorophyll, site of photosynthesis.
Q20. The non-membrane-bound organelles are
A) Mitochondria
B) Chloroplasts
C) Ribosomes ✅
D) ER
Explanation: Ribosomes are non-membranous, present in both prokaryotes & eukaryotes.
Q21. The outermost covering of animal cell is
A) Cell wall
B) Plasma membrane ✅
C) Cuticle
D) Glycocalyx
Explanation: Animal cells lack a cell wall; they are covered by a plasma membrane.
Q22. The organelle for lipid synthesis is
A) RER
B) SER ✅
C) Golgi body
D) Lysosome
Explanation: Smooth Endoplasmic Reticulum (SER) is the site of lipid synthesis.
Q23. The basic structural and functional unit of chromosomes is
A) Chromatin
B) DNA
C) Nucleosome ✅
D) Histone
Explanation: Nucleosome = DNA wrapped around histone proteins, unit of chromosome.
Q24. Centrioles are absent in
A) Plant cells ✅
B) Animal cells
C) Algae
D) Protists
Explanation: Plant cells generally lack centrioles, present in animal cells.
Q25. The organelle called “cell’s stomach” is
A) Ribosome
B) Lysosome ✅
C) Vacuole
D) ER
Explanation: Lysosomes digest waste and unwanted materials, acting like the stomach of the cell.
🔬 Cell Structure and Function — Cell: The Unit of Life
Part 2 (Q26–Q50)
Q26. The functional unit of heredity is
A) DNA
B) Gene ✅
C) Chromosome
D) RNA
Explanation: Gene is the functional unit of heredity, coding for proteins/traits.
Q27. Which organelle is the “ribosome factory”?
A) Nucleus
B) Nucleolus ✅
C) ER
D) Golgi apparatus
Explanation: Nucleolus is the site of rRNA synthesis and ribosome assembly.
Q28. The “control center of cell” is
A) Mitochondria
B) Nucleus ✅
C) Golgi apparatus
D) ER
Explanation: Nucleus controls all cell activities by regulating gene expression.
Q29. Which of the following is absent in prokaryotes?
A) DNA
B) Nucleus ✅
C) Ribosome
D) Plasma membrane
Explanation: Prokaryotes lack a true nucleus but have DNA, ribosomes, and membranes.
Q30. The plasma membrane is mainly composed of
A) DNA and proteins
B) Lipids and proteins ✅
C) Proteins and carbohydrates
D) RNA and proteins
Explanation: Plasma membrane is a lipid bilayer with proteins and carbohydrates.
Q31. The cell wall of fungi is made up of
A) Cellulose
B) Chitin ✅
C) Pectin
D) Glycogen
Explanation: Fungal cell wall is made of chitin and glucans.
Q32. The cell wall of bacteria is made up of
A) Cellulose
B) Chitin
C) Peptidoglycan ✅
D) Protein
Explanation: Bacterial cell wall contains peptidoglycan (murein).
Q33. The site of synthesis of rRNA is
A) Ribosomes
B) Nucleolus ✅
C) Mitochondria
D) Golgi apparatus
Explanation: Nucleolus synthesizes rRNA and assembles ribosomal subunits.
Q34. Which organelle is called the “cell’s post office”?
A) ER
B) Golgi apparatus ✅
C) Lysosome
D) Vacuole
Explanation: Golgi bodies package, modify, and transport cellular products like a post office.
Q35. The double-membrane organelles are
A) Mitochondria and chloroplasts ✅
B) Ribosomes and lysosomes
C) Golgi body and ER
D) Peroxisome and vacuole
Explanation: Mitochondria and chloroplasts are double-membrane-bound with their own DNA.
Q36. Which organelle is rich in hydrolytic enzymes?
A) Ribosome
B) Lysosome ✅
C) Golgi body
D) ER
Explanation: Lysosomes have acid hydrolases for intracellular digestion.
Q37. The function of SER is
A) Protein synthesis
B) Lipid synthesis ✅
C) DNA replication
D) Cell division
Explanation: Smooth Endoplasmic Reticulum synthesizes lipids and steroids.
Q38. The function of RER is
A) Lipid synthesis
B) Protein synthesis ✅
C) Detoxification
D) Photosynthesis
Explanation: Rough ER, studded with ribosomes, synthesizes proteins.
Q39. The site of photosynthesis is
A) Mitochondria
B) Chloroplast ✅
C) Ribosome
D) Golgi body
Explanation: Chloroplast contains chlorophyll and performs photosynthesis.
Q40. Which structure regulates the entry and exit of substances in a cell?
A) ER
B) Plasma membrane ✅
C) Lysosome
D) Ribosome
Explanation: Plasma membrane is selectively permeable, controlling transport.
Q41. Which of the following is called the “skeleton of the cell”?
A) Nucleus
B) Cytoskeleton ✅
C) ER
D) Mitochondria
Explanation: Cytoskeleton (microtubules, microfilaments) provides shape, support, movement.
Q42. Microtubules are made of
A) Tubulin protein ✅
B) Actin
C) Myosin
D) Keratin
Explanation: Microtubules are composed of tubulin dimers.
Q43. Microfilaments are made of
A) Actin ✅
B) Tubulin
C) Keratin
D) Collagen
Explanation: Microfilaments are thin filaments made of actin protein.
Q44. Which organelle is called the “polymorphic organelle”?
A) Lysosome ✅
B) Ribosome
C) ER
D) Golgi apparatus
Explanation: Lysosomes show polymorphism — primary, secondary, residual bodies.
Q45. Which structure is responsible for spindle formation in animal cells?
A) Nucleolus
B) Centrosome ✅
C) Ribosome
D) Lysosome
Explanation: Centrosome (with centrioles) forms the spindle apparatus during cell division.
Q46. The 70S ribosomes are found in
A) Eukaryotic cytoplasm
B) Prokaryotes ✅
C) Nucleus
D) Lysosome
Explanation: Prokaryotes have 70S ribosomes (smaller than 80S of eukaryotes).
Q47. The 80S ribosomes are found in
A) Prokaryotes
B) Eukaryotic cytoplasm ✅
C) Chloroplast
D) Mitochondria
Explanation: Cytoplasm of eukaryotic cells has 80S ribosomes.
Q48. The 70S ribosomes are also found in
A) Cytoplasm of eukaryotes
B) Chloroplasts and mitochondria ✅
C) Lysosomes
D) Vacuoles
Explanation: Mitochondria and chloroplasts have prokaryote-like 70S ribosomes.
Q49. Which organelle is called the “detox center” of cell?
A) RER
B) SER ✅
C) Golgi body
D) Lysosome
Explanation: SER detoxifies drugs and poisons in liver cells.
Q50. The site of aerobic respiration is
A) Chloroplast
B) Ribosome
C) Mitochondria ✅
D) ER
Explanation: Mitochondria carry out aerobic respiration, producing ATP.
🔬 Cell Structure and Function — Cell: The Unit of Life
Part 3 (Q51–Q75)
Q51. The double-membrane organelles with cristae are
A) Golgi bodies
B) Chloroplasts
C) Mitochondria ✅
D) Ribosomes
Explanation: Mitochondria are double-membrane-bound, inner membrane forms cristae for ATP synthesis.
Q52. The photosynthetic pigments are located in
A) Stroma
B) Thylakoid membranes ✅
C) Outer membrane
D) Matrix
Explanation: Chlorophyll and pigments are embedded in thylakoid membranes of chloroplasts.
Q53. The disc-shaped structures in chloroplasts are
A) Cristae
B) Thylakoids ✅
C) Grana
D) Vesicles
Explanation: Thylakoids are disc-like membranous sacs, stacked into grana.
Q54. The space surrounding grana in chloroplast is
A) Cristae
B) Matrix
C) Stroma ✅
D) Lumen
Explanation: Stroma is the matrix of chloroplast containing enzymes for dark reaction.
Q55. The “ATP factory” of the cell is
A) Chloroplast
B) Mitochondria ✅
C) Golgi apparatus
D) Ribosome
Explanation: Mitochondria produce ATP via oxidative phosphorylation.
Q56. The green pigment chlorophyll is present in
A) Cytoplasm
B) Grana thylakoids ✅
C) Stroma
D) Ribosomes
Explanation: Chlorophyll resides in the thylakoid membranes.
Q57. The storage sacs in plant cells are
A) Vacuoles ✅
B) Lysosomes
C) Plastids
D) Ribosomes
Explanation: Vacuoles store water, ions, pigments, waste, etc., in plant cells.
Q58. In mature plant cells, vacuoles are surrounded by
A) Plasma membrane
B) Cell wall
C) Tonoplast ✅
D) Middle lamella
Explanation: The vacuole is bounded by a specialized membrane called tonoplast.
Q59. The region between two daughter nuclei in cytokinesis is called
A) Cell wall
B) Cell plate ✅
C) Middle lamella
D) Spindle
Explanation: In plant cytokinesis, a cell plate forms the new dividing wall.
Q60. The region between two adjacent plant cells that holds them together is
A) Plasma membrane
B) Middle lamella ✅
C) Plasmodesmata
D) Tonoplast
Explanation: Middle lamella (rich in calcium pectate) cements adjacent plant cells.
Q61. The connections between adjacent plant cells are
A) Gap junctions
B) Tight junctions
C) Plasmodesmata ✅
D) Desmosomes
Explanation: Plasmodesmata are cytoplasmic bridges connecting adjacent plant cells.
Q62. The connections between adjacent animal cells are
A) Plasmodesmata
B) Tight junctions, gap junctions, desmosomes ✅
C) Middle lamella
D) Tonoplast
Explanation: Animal cells communicate via tight junctions, gap junctions, and desmosomes.
Q63. Chromatin that is transcriptionally active is
A) Heterochromatin
B) Euchromatin ✅
C) Nucleolus
D) Histone
Explanation: Euchromatin is loosely packed, light-staining, and transcriptionally active.
Q64. The inactive, condensed chromatin is
A) Euchromatin
B) Heterochromatin ✅
C) Nucleolus
D) Centromere
Explanation: Heterochromatin is tightly packed, transcriptionally inactive.
Q65. The centromere is associated with
A) Nucleolus
B) Chromosome ✅
C) Ribosome
D) Histone
Explanation: Centromere is the primary constriction on a chromosome, where spindle attaches.
Q66. The ends of chromosomes are called
A) Centromeres
B) Kinetochores
C) Telomeres ✅
D) Chromatids
Explanation: Telomeres are DNA-protein complexes that protect chromosome ends.
Q67. The smallest functional unit of chromosome packaging is
A) Histone
B) Nucleosome ✅
C) Solenoid
D) Chromatin
Explanation: Nucleosome = DNA wrapped around histone octamer.
Q68. The barrel-shaped organelles near nucleus are
A) Ribosomes
B) Centrioles ✅
C) Lysosomes
D) Nucleolus
Explanation: Centrioles are barrel-shaped, organizing spindle fibres in animal cells.
Q69. The site of ribosome attachment in RER is
A) Proteins
B) tRNA
C) Ribophorin proteins ✅
D) Actin
Explanation: Ribosomes attach to RER membrane via ribophorin proteins.
Q70. The main function of mitochondria is
A) Lipid synthesis
B) Protein synthesis
C) ATP production ✅
D) Photosynthesis
Explanation: Mitochondria generate ATP through cellular respiration.
Q71. The mitochondrial matrix contains
A) Enzymes, DNA, ribosomes ✅
B) Thylakoids
C) Cristae
D) Middle lamella
Explanation: Matrix contains enzymes for Krebs cycle, mitochondrial DNA, and 70S ribosomes.
Q72. DNA in prokaryotes is
A) Linear
B) Circular ✅
C) Both linear and circular
D) None
Explanation: Prokaryotes have circular, naked DNA.
Q73. The eukaryotic cell DNA is
A) Circular
B) Linear ✅
C) Helical and circular
D) None
Explanation: Eukaryotic nuclear DNA is linear, chromatin-bound.
Q74. The “protein factory of cell” is
A) Ribosome ✅
B) ER
C) Golgi
D) Lysosome
Explanation: Ribosomes synthesize proteins; hence called protein factories.
Q75. The organelle responsible for autophagy is
A) Ribosome
B) Lysosome ✅
C) Mitochondria
D) Nucleus
Explanation: Lysosomes degrade old organelles in a process called autophagy.
🔬 Cell Structure and Function — Cell: The Unit of Life
Part 4 (Q76–Q100)
Q76. The structure that forms spindle fibres during cell division is
A) Nucleolus
B) Ribosomes
C) Centrioles ✅
D) Golgi bodies
Explanation: Centrioles form spindle fibres in animal cells for chromosome movement.
Q77. The semi-autonomous organelles are
A) Golgi body, ER
B) Lysosome, Vacuole
C) Mitochondria, Chloroplast ✅
D) Ribosome, Centriole
Explanation: Mitochondria and chloroplasts have DNA, RNA, ribosomes — they self-replicate.
Q78. The organelle responsible for photorespiration is
A) Peroxisome ✅
B) Ribosome
C) Chloroplast
D) Lysosome
Explanation: Peroxisomes participate in photorespiration and fatty acid oxidation.
Q79. The main site of glycolysis is
A) Nucleus
B) Cytoplasm ✅
C) Mitochondria
D) Chloroplast
Explanation: Glycolysis occurs in cytoplasm (breakdown of glucose).
Q80. The main site of Krebs cycle is
A) Cytoplasm
B) Chloroplast
C) Mitochondrial matrix ✅
D) Nucleus
Explanation: Krebs cycle enzymes are located in the mitochondrial matrix.
Q81. Oxidative phosphorylation occurs in
A) Cytoplasm
B) Inner mitochondrial membrane ✅
C) Nucleus
D) ER
Explanation: Electron transport chain and ATP synthesis occur on the inner mitochondrial membrane.
Q82. The enzyme ATP synthase is located in
A) Cytoplasm
B) Thylakoid membrane & inner mitochondrial membrane ✅
C) Ribosome
D) Golgi
Explanation: ATP synthase functions in chloroplast thylakoids and mitochondrial cristae.
Q83. The dark reaction of photosynthesis occurs in
A) Grana
B) Stroma ✅
C) Thylakoid lumen
D) Outer membrane
Explanation: The Calvin cycle (dark reaction) takes place in stroma of chloroplast.
Q84. The light reaction of photosynthesis occurs in
A) Stroma
B) Thylakoid membranes ✅
C) Cytoplasm
D) Nucleus
Explanation: Light-dependent reactions occur in thylakoid membranes.
Q85. The universal energy currency of cell is
A) DNA
B) RNA
C) ATP ✅
D) GTP
Explanation: ATP is called the energy currency of the cell.
Q86. Which structure is absent in animal cells but present in plant cells?
A) Nucleus
B) Cell wall ✅
C) Ribosome
D) Plasma membrane
Explanation: Plant cells have a rigid cell wall, absent in animals.
Q87. In eukaryotes, DNA is packaged with
A) Tubulin
B) Histone proteins ✅
C) Actin
D) Myosin
Explanation: Histone proteins help package eukaryotic DNA into nucleosomes.
Q88. The membrane system that synthesizes proteins is
A) SER
B) RER ✅
C) Golgi body
D) Lysosome
Explanation: RER with ribosomes attached is the site of protein synthesis.
Q89. The main constituent of plasma membrane is
A) Phospholipids ✅
B) Proteins only
C) Carbohydrates only
D) Nucleic acids
Explanation: Plasma membrane is a phospholipid bilayer with proteins.
Q90. Which organelle detoxifies alcohol in liver cells?
A) Lysosome
B) Peroxisome ✅
C) Golgi body
D) SER
Explanation: Peroxisomes and SER detoxify harmful substances in liver.
Q91. Which organelle is absent in prokaryotes?
A) Ribosome
B) Nucleus ✅
C) Plasma membrane
D) Cytoplasm
Explanation: Prokaryotes lack a true nucleus and membrane-bound organelles.
Q92. The average size of prokaryotic ribosomes is
A) 80S
B) 70S ✅
C) 60S
D) 50S
Explanation: Prokaryotes have 70S ribosomes (50S + 30S subunits).
Q93. The ribosomes of eukaryotic cytoplasm are
A) 70S
B) 80S ✅
C) 60S
D) 50S
Explanation: Eukaryotic cytoplasm contains 80S ribosomes (60S + 40S).
Q94. Cell wall in prokaryotes is absent in
A) Bacteria
B) Archaea
C) Mycoplasma ✅
D) Cyanobacteria
Explanation: Mycoplasma lacks a cell wall, only a plasma membrane.
Q95. The main component of bacterial cell wall is
A) Cellulose
B) Chitin
C) Peptidoglycan ✅
D) Pectin
Explanation: Peptidoglycan is the major component of bacterial cell wall.
Q96. The protein channels in membranes are mainly made of
A) Carbohydrates
B) Integral proteins ✅
C) Peripheral proteins
D) Sterols
Explanation: Integral proteins act as channels and carriers in membranes.
Q97. The chromosome number in prokaryotes is usually
A) Multiple
B) One, circular ✅
C) Two, linear
D) Variable
Explanation: Most prokaryotes have a single, circular chromosome.
Q98. The main difference between prokaryotic and eukaryotic ribosomes is
A) Number of proteins
B) Size: 70S vs 80S ✅
C) Both are identical
D) Function differs
Explanation: Prokaryotes = 70S ribosomes, Eukaryotes = 80S ribosomes.
Q99. The plant cell vacuole is filled with
A) Starch
B) Cell sap ✅
C) Air
D) Enzymes
Explanation: Vacuoles contain cell sap (water, ions, sugars, pigments, waste).
Q100. The barrier between adjacent plant cells for cytoplasmic exchange is
A) Plasmodesmata ✅
B) Gap junction
C) Middle lamella
D) Tonoplast
Explanation: Plasmodesmata are cytoplasmic connections for cell-to-cell transport.
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