50 MCQ on Cell: The smallest unit of life

🟢 EASY (20 Questions)

1. Who discovered the cell?
   a) Robert Koch
   b) Anton van Leeuwenhoek
   c) Robert Hooke
   d) Matthias Schleiden
   Answer: c) Robert Hooke
   Explanation: He observed cork cells under a microscope in 1665 and coined the term “cell.”
2. The basic structural and functional unit of life is the:
   a) Atom
   b) Molecule
   c) Organelle
   d) Cell
   Answer: d) Cell
   Explanation: All living organisms are made of cells which perform life functions.
3. Which of the following organisms is unicellular?
   a) Amoeba
   b) Earthworm
   c) Mango tree
   d) Human
   Answer: a) Amoeba
   Explanation: Amoeba is made up of a single cell.
4. Cell wall is absent in:
   a) Bacteria
   b) Plant cells
   c) Animal cells
   d) Fungi
   Answer: c) Animal cells
   Explanation: Only plant cells and some microorganisms have a cell wall.
5. The jelly-like substance present inside the cell is:
   a) Nucleoplasm
   b) Cytoplasm
   c) Protoplasm
   d) Plasma
   Answer: b) Cytoplasm
   Explanation: Cytoplasm surrounds organelles and is the site for many cellular processes.
6. Which organelle is called the ‘powerhouse of the cell’?
   a) Chloroplast
   b) Golgi apparatus
   c) Mitochondria
   d) Nucleus
   Answer: c) Mitochondria
   Explanation: It produces energy in the form of ATP.
7. Which structure controls the activities of the cell?
   a) Ribosome
   b) Cytoplasm
   c) Nucleus
   d) Endoplasmic reticulum
   Answer: c) Nucleus
   Explanation: The nucleus contains DNA and regulates cell functions.
8. Which organelle is present only in plant cells?
   a) Mitochondria
   b) Chloroplast
   c) Ribosome
   d) Lysosome
   Answer: b) Chloroplast
   Explanation: Chloroplasts carry out photosynthesis and are found in plants only.
9. Ribosomes are the site of:
   a) Photosynthesis
   b) Protein synthesis
   c) Respiration
   d) DNA replication
   Answer: b) Protein synthesis
   Explanation: Ribosomes assemble amino acids into proteins.
10. The plasma membrane is composed mainly of:
    a) DNA and RNA
    b) Proteins and lipids
    c) Cellulose
    d) Carbohydrates
    Answer: b) Proteins and lipids
    Explanation: The lipid bilayer forms the structural framework of the membrane.
11. Which of these is found in prokaryotes but not in eukaryotes?
    a) Cell membrane
    b) Ribosomes
    c) Nucleus
    d) DNA
    Answer: c) Nucleus
    Explanation: Prokaryotes lack a true nucleus.
12. What is the function of the cell wall?
    a) Protection and support
    b) Respiration
    c) Protein synthesis
    d) Transport of materials
    Answer: a) Protection and support
    Explanation: It provides structure and protects plant cells.
13. Which part of the cell helps in cell division?
    a) Nucleus
    b) Centrioles
    c) Golgi body
    d) Mitochondria
    Answer: b) Centrioles
    Explanation: Centrioles help in organizing the mitotic spindle during cell division.
14. Which organelle is responsible for digestion within the cell?
    a) Ribosome
    b) Lysosome
    c) Mitochondria
    d) Nucleus
    Answer: b) Lysosome
    Explanation: Lysosomes contain digestive enzymes.
15. Which organelle modifies and packages proteins?
    a) Endoplasmic reticulum
    b) Golgi apparatus
    c) Ribosome
    d) Vacuole
    Answer: b) Golgi apparatus
    Explanation: Golgi apparatus processes and packages proteins.
16. What is the fluid-filled space in plant cells called?
    a) Nucleus
    b) Vacuole
    c) Cytoplasm
    d) Golgi body
    Answer: b) Vacuole
    Explanation: The central vacuole stores water and nutrients in plant cells.
17. DNA is mainly located in:
    a) Ribosomes
    b) Nucleus
    c) Cytoplasm
    d) Mitochondria
    Answer: b) Nucleus
    Explanation: DNA is contained in the chromosomes within the nucleus.
18. Plant cells are different from animal cells because they have:
    a) Mitochondria
    b) Ribosomes
    c) Chloroplasts
    d) Nucleus
    Answer: c) Chloroplasts
    Explanation: Chloroplasts enable photosynthesis in plants.
19. Which of the following is a double membrane-bound organelle?
    a) Ribosome
    b) Golgi body
    c) Lysosome
    d) Mitochondria
    Answer: d) Mitochondria
    Explanation: Mitochondria have an outer and an inner membrane.
20. Which structure in the nucleus is responsible for making ribosomes?
    a) Chromatin
    b) Nucleolus
    c) Nuclear envelope
    d) Centrosome
    Answer: b) Nucleolus
    Explanation: Nucleolus synthesizes ribosomal RNA.

🟡 MODERATE (20 Questions)

21. Which organelle is continuous with the nuclear membrane?
    a) Golgi apparatus
    b) Endoplasmic reticulum
    c) Lysosome
    d) Vacuole
    Answer: b) Endoplasmic reticulum
    Explanation: ER is connected to the outer membrane of the nucleus.
22. Which is not a part of the cell theory?
    a) All living things are made of cells
    b) All cells arise from pre-existing cells
    c) Cells are the basic unit of life
    d) All cells have a nucleus
    Answer: d) All cells have a nucleus
    Explanation: Prokaryotic cells do not have a nucleus.
23. Plasmodesmata are found in:
    a) Animal cells
    b) Fungal cells
    c) Plant cells
    d) Bacterial cells
    Answer: c) Plant cells
    Explanation: They are channels between plant cell walls.
24. The smooth endoplasmic reticulum is involved in:
    a) Protein synthesis
    b) Lipid synthesis
    c) Cell division
    d) DNA replication
    Answer: b) Lipid synthesis
    Explanation: SER synthesizes lipids and steroids.
25. Cristae are present in which organelle?
    a) Nucleus
    b) Chloroplast
    c) Mitochondria
    d) Lysosome
    Answer: c) Mitochondria
    Explanation: Cristae increase surface area for ATP production.
26. Which statement is true about prokaryotic cells?
    a) They have a membrane-bound nucleus
    b) They are always multicellular
    c) They contain 80S ribosomes
    d) They lack membrane-bound organelles
    Answer: d) They lack membrane-bound organelles
    Explanation: Prokaryotic cells do not have organelles like mitochondria.
27. The primary function of peroxisomes is to:
    a) Digest cellular waste
    b) Break down hydrogen peroxide
    c) Synthesize proteins
    d) Store nutrients
    Answer: b) Break down hydrogen peroxide
    Explanation: Peroxisomes contain catalase to decompose H₂O₂.
28. Which of the following is a membrane-less organelle?
    a) Nucleus
    b) Nucleolus
    c) Mitochondria
    d) Lysosome
    Answer: b) Nucleolus
    Explanation: The nucleolus is not bounded by a membrane.
29. In plant cells, cytokinesis occurs by:
    a) Cleavage furrow
    b) Spindle fiber formation
    c) Cell plate formation
    d) Meiosis
    Answer: c) Cell plate formation
    Explanation: A cell plate forms in the middle during plant cytokinesis.
30. Tonoplast is a membrane associated with:
    a) Nucleus
    b) Lysosome
    c) Vacuole
    d) Mitochondria
    Answer: c) Vacuole
    Explanation: Tonoplast surrounds the central vacuole in plant cells.
31. Which structure helps bacteria attach to surfaces?
    a) Capsule
    b) Cell wall
    c) Pili
    d) Ribosome
    Answer: c) Pili
    Explanation: Pili are hair-like structures used for attachment and sometimes conjugation.
32. What is the function of the nuclear pore complex?
    a) Protein synthesis
    b) ATP production
    c) Transport between nucleus and cytoplasm
    d) DNA replication
    Answer: c) Transport between nucleus and cytoplasm
    Explanation: Nuclear pores regulate movement of materials in/out of the nucleus.
33. Mitochondrial DNA is:
    a) Absent
    b) Linear
    c) Circular
    d) Double-stranded linear
    Answer: c) Circular
    Explanation: Like prokaryotic DNA, mitochondrial DNA is circular.
34. Which organelle is also known as the ‘suicide bag’?
    a) Lysosome
    b) Golgi body
    c) Nucleus
    d) Endoplasmic reticulum
    Answer: a) Lysosome
    Explanation: Lysosomes contain enzymes that can digest the cell itself.
35. Which organelle is involved in the formation of glycoproteins?
    a) Ribosome
    b) Mitochondria
    c) Golgi apparatus
    d) Nucleus
    Answer: c) Golgi apparatus
    Explanation: Golgi bodies modify proteins by adding sugar molecules to form glycoproteins.
36. Which cell organelle has its own DNA, besides the nucleus?
    a) Ribosome
    b) Mitochondria
    c) Golgi complex
    d) Lysosome
    Answer: b) Mitochondria
    Explanation: Mitochondria contain their own DNA and replicate independently.
37. Which of the following is absent in mature RBCs (Red Blood Cells)?
    a) Mitochondria
    b) Ribosomes
    c) Nucleus
    d) All of these
    Answer: d) All of these
    Explanation: Mature mammalian RBCs lack all organelles to maximize space for hemoglobin.
38. Which of the following organelles is involved in autophagy?
    a) Golgi apparatus
    b) Lysosome
    c) Vacuole
    d) Peroxisome
    Answer: b) Lysosome
    Explanation: Lysosomes digest damaged cell components during autophagy.
39. Which part of the cytoskeleton is responsible for cell shape and movement?
    a) Ribosomes
    b) Microfilaments
    c) Golgi vesicles
    d) Nucleus
    Answer: b) Microfilaments
    Explanation: Microfilaments are actin filaments that help maintain cell shape and assist in movement.
40. What is the main component of the cell wall in fungi?
    a) Cellulose
    b) Chitin
    c) Pectin
    d) Peptidoglycan
    Answer: b) Chitin
    Explanation: Fungal cell walls are mainly composed of chitin, not cellulose like in plants.

🔴 HARD (10 Questions)

41. Mesosomes in prokaryotes are functionally analogous to:
    a) Lysosomes
    b) Nucleus
    c) Mitochondria
    d) Ribosomes
    Answer: c) Mitochondria
    Explanation: Mesosomes are invaginations of the plasma membrane involved in respiration.
42. The 80S ribosomes are found in:
    a) Prokaryotes only
    b) Mitochondria
    c) Cytoplasm of eukaryotes
    d) Nucleus
    Answer: c) Cytoplasm of eukaryotes
    Explanation: Eukaryotic cytoplasm contains 80S ribosomes; prokaryotes have 70S.
43. Which of the following is correct about the fluid mosaic model of the plasma membrane?
    a) Proteins are rigidly fixed
    b) Lipids form a rigid matrix
    c) Proteins float in a sea of lipids
    d) Carbohydrates are buried in lipid layers
    Answer: c) Proteins float in a sea of lipids
    Explanation: The model describes proteins embedded in or on a flexible lipid bilayer.
44. Which statement is true about chromatin?
    a) Found only in prokaryotes
    b) Contains DNA and proteins
    c) Formed only during cell division
    d) Does not condense into chromosomes
    Answer: b) Contains DNA and proteins
    Explanation: Chromatin is a DNA-protein complex in the nucleus.
45. Which of the following processes occurs in the nucleolus?
    a) DNA replication
    b) mRNA synthesis
    c) rRNA synthesis
    d) Protein synthesis
    Answer: c) rRNA synthesis
    Explanation: The nucleolus produces ribosomal RNA and assembles ribosomal subunits.
46. What is the role of the glycoproteins on the plasma membrane?
    a) Structural support
    b) Energy production
    c) Cell recognition
    d) DNA transport
    Answer: c) Cell recognition
    Explanation: Glycoproteins act as markers for cell-cell recognition.
47. The outer membrane of mitochondria is:
    a) Impermeable
    b) Semi-permeable
    c) Selectively permeable
    d) Freely permeable to small molecules
    Answer: d) Freely permeable to small molecules
    Explanation: The outer membrane has porins that allow small molecules to pass freely.
48. Which of the following organelles is associated with the synthesis of steroid hormones?
    a) Rough ER
    b) Smooth ER
    c) Mitochondria
    d) Ribosomes
    Answer: b) Smooth ER
    Explanation: The smooth ER is involved in the synthesis of lipids and steroids.
49. Which is the correct sequence of events during protein synthesis?
    a) Transcription → Translation → Transport
    b) Translation → Transcription → Transport
    c) Transport → Transcription → Translation
    d) Transcription → Transport → Translation
    Answer: a) Transcription → Translation → Transport
    Explanation: DNA is transcribed into mRNA, which is translated into protein, then transported.
50. In prokaryotic cells, the genetic material is present in:
    a) Membrane-bound nucleus
    b) Nucleoid region
    c) Mitochondria
    d) Nucleolus
    Answer: b) Nucleoid region
    Explanation: Prokaryotes lack a nucleus, and DNA resides in the nucleoid.