The Fundamental Unit of Life – MCQs with Answers and Explanations
Class 9 • Biology
Chapter 5: The Fundamental Unit of Life — 50 Topic-wise MCQs
Instructions: There are 50 MCQs divided into 10 topic sections. Each question has four options (A–D), the correct answer, and a brief explanation to clear concepts as per NCERT Class 9 Biology Chapter 5.
Topic: Discovery of Cell & Microscopy
Q1. Who first observed cells in cork and coined the term 'cell'?
Answer: B — Robert Hooke.
Hooke (1665) examined thin slices of cork and described compartments as "cells" (monastic cells). Leeuwenhoek observed living cells later.
Q2. Which microscope would you use to observe the surface structure of a cell in greatest detail?
Answer: D — Scanning electron microscope (SEM).
SEM gives detailed 3D images of cell surfaces. TEM is for internal ultrastructure.
Q3. The resolving power (ability to distinguish two close points) of an ordinary light microscope is about:
Answer: B — 200–300 nm.
Light microscopes are limited by wavelength of visible light; fine structures like ribosomes (~20 nm) are below this limit.
Q4. Which scientist improved the microscope and described single-celled organisms (which he called 'animalcules')?
Answer: B — Anton van Leeuwenhoek.
Leeuwenhoek made powerful simple microscopes and observed bacteria and protozoa (animalcules).
Q5. Which of the following techniques enhances contrast of transparent specimens without staining?
Answer: B — Phase-contrast microscopy.
Phase-contrast converts phase shifts in light passing through transparent specimens into brightness differences, useful for live cells.
Topic: Cell Theory & Types of Cells
Q6. Which statement is NOT part of modern cell theory?
Answer: D — All cells contain mitochondria.
Not all cells have mitochondria (eg. prokaryotes lack membrane-bound organelles). The other statements are core cell theory principles.
Q7. Prokaryotic cells differ from eukaryotic cells in that prokaryotes:
Answer: B — have no membrane-bound organelles.
Prokaryotes lack nucleus and membrane-bound organelles; they are unicellular and have DNA in nucleoid region.
Q8. Which of these organisms is eukaryotic?
Answer: C — Paramecium.
Paramecium is a single-celled eukaryote with a nucleus and organelles; the others are bacteria (prokaryotes).
Q9. Which scientist proposed that plants are made of cells?
Answer: B — Matthias Schleiden.
Schleiden (1838) concluded that plant tissues are made of cells; Theodor Schwann later extended similar ideas to animals.
Q10. "Omnis cellula e cellula" means:
Answer: B — All cells come from pre-existing cells.
This phrase was popularised by Rudolf Virchow, emphasising cell division as the source of new cells.
Topic: Cell Structure — Cell Wall, Cell Membrane & Nucleus
Q11. The major component of plant cell wall is:
Answer: A — Cellulose.
Plant cell walls are primarily cellulose (a polysaccharide). Chitin is in fungal cell walls; peptidoglycan in bacterial walls.
Q12. Which structure controls entry and exit of substances in a cell?
Answer: B — Cell membrane.
The plasma membrane is selectively permeable and regulates transport; cell wall provides support but is not selectively permeable.
Q13. The nucleus is responsible for:
Answer: C — Storage of genetic information and control of cell activities.
Nucleus contains DNA, directs protein synthesis and regulates cell functions; protein synthesis occurs in cytoplasm and ER.
Q14. Which of the following is absent in bacterial cells?
Answer: C — Nucleus.
Bacteria lack a true nucleus; their genetic material lies in the nucleoid region. They have ribosomes and cell walls (peptidoglycan).
Q15. Nuclear membrane disappears during:
Answer: B — Prophase of mitosis.
During prophase the nuclear envelope breaks down, allowing spindle fibres to interact with chromosomes.
Topic: Cell Organelles — Structure & Function
Q16. Chloroplasts are the sites of:
Answer: C — Photosynthesis.
Chloroplasts contain chlorophyll which captures light energy to synthesise glucose.
Q17. Which organelle is known as the powerhouse of the cell?
Answer: B — Mitochondrion.
Mitochondria produce ATP through cellular respiration, supplying energy for cellular processes.
Q18. Ribosomes are the sites of:
Answer: B — Protein synthesis.
Ribosomes translate mRNA into polypeptides; they may be free or attached to rough ER.
Q19. Which organelle helps in modification and packaging of proteins?
Answer: A — Golgi apparatus.
Golgi receives vesicles from ER, modifies proteins (eg. glycosylation) and sorts them into vesicles for secretion or delivery.
Q20. Which organelle contains digestive enzymes to break down cellular waste?
Answer: A — Lysosome.
Lysosomes contain hydrolytic enzymes for intracellular digestion and recycling of materials.
Topic: Cell Membrane & Transport
Q21. The fluid mosaic model describes the structure of:
Answer: B — Cell membrane.
The fluid mosaic model describes a phospholipid bilayer with embedded proteins that move laterally, making the membrane fluid and mosaic-like.
Q22. Movement of water across a selectively permeable membrane is called:
Answer: B — Osmosis.
Osmosis is water movement from region of higher water potential to lower water potential through a semipermeable membrane.
Q23. Which process requires energy (ATP) to move substances against a concentration gradient?
Answer: C — Active transport.
Active transport uses carrier proteins and ATP to move ions or molecules from low to high concentration.
Q24. In which solution will an animal cell swell and possibly burst?
Answer: C — Hypotonic solution.
In hypotonic external medium, water enters the cell by osmosis causing swelling and potential lysis in animal cells (no cell wall).
Q25. Which of the following is an example of facilitated diffusion?
Answer: A — Glucose transport into cells via carrier proteins.
Facilitated diffusion uses specific membrane proteins to help polar molecules like glucose cross the membrane down their concentration gradient without ATP.
Topic: Vacuoles, Golgi Apparatus & Endoplasmic Reticulum
Q26. The rough endoplasmic reticulum is studded with:
Answer: B — Ribosomes.
Rough ER has ribosomes on its surface for synthesis of proteins destined for secretion or membranes.
Q27. Which cellular structure stores water and maintains turgor in plant cells?
Answer: B — Large central vacuole.
Central vacuole stores water, ions and maintains turgor pressure supporting cell rigidity.
Q28. Secretory vesicles are formed from the:
Answer: B — Golgi apparatus.
Golgi packages modified proteins into vesicles that bud off for secretion or delivery to organelles.
Q29. Which statement about smooth endoplasmic reticulum (SER) is correct?
Answer: B — SER is associated with lipid synthesis and detoxification.
SER lacks ribosomes and functions in lipid metabolism and detoxification in liver cells.
Q30. Tonoplast is the membrane that surrounds the:
Answer: C — Central vacuole.
Tonoplast is the vacuolar membrane separating vacuolar contents from cytoplasm.
Topic: Cell Division — Basic Concepts
Q31. Mitosis results in the formation of:
Answer: B — Two genetically identical daughter cells.
Mitosis produces two daughter cells genetically identical to parent, maintaining chromosome number.
Q32. Which phase of cell cycle is where DNA replication occurs?
Answer: B — S phase.
S phase (synthesis) is when DNA is replicated so that each daughter cell receives a complete genome.
Q33. Cytokinesis is the process of:
Answer: B — Division of cytoplasm to form daughter cells.
Cytokinesis follows karyokinesis (nuclear division) and physically separates the two daughter cells.
Q34. Which of these events occurs during prophase?
Answer: B — Chromosomes become visible and nuclear membrane breaks down.
Prophase involves condensation of chromatin into visible chromosomes and dissolution of nuclear envelope.
Q35. Which cells undergo meiosis instead of mitosis?
Answer: C — Germ cells producing gametes.
Meiosis produces haploid gametes (sperm and egg) with genetic variation; somatic cells divide by mitosis.
Topic: Plant vs Animal Cells
Q36. Which feature is found in plant cells but NOT in animal cells?
Answer: B — Cell wall.
Plant cells have a rigid cell wall made of cellulose; animal cells lack a cell wall and have only a plasma membrane.
Q37. Which organelle in plant cells captures light energy?
Answer: B — Chloroplast.
Chloroplasts contain chlorophyll and are responsible for photosynthesis in plants.
Q38. Animal cells differ from plant cells because animal cells:
Answer: C — often have centrioles involved in cell division.
Centrioles are typically present in animal cells and play a role in forming spindle fibres during mitosis.
Q39. Which is TRUE about vacuoles in plant and animal cells?
Answer: C — Plant cells have a large central vacuole while animal cells have small or absent vacuoles.
Plant vacuole stores water and solutes; animal cells may have small vacuoles/vesicles for storage but not a single large one.
Q40. Photosynthesis occurs in which cell type?
Answer: B — Leaf mesophyll cell.
Mesophyll cells in leaves are rich in chloroplasts and are the main site of photosynthesis.
Topic: Specialised Cells & Tissues
Q41. Root hair cells are specialised for:
Answer: B — Absorption of water and minerals.
Root hair cells increase surface area for efficient absorption from soil and often have many mitochondria for active uptake.
Q42. Red blood cells are biconcave in shape to:
Answer: B — Increase surface area for gas exchange and flexibility.
Biconcave shape increases surface area-to-volume ratio for O2/CO2 exchange and helps RBCs pass through narrow capillaries.
Q43. Neurons are long and branched to:
Answer: B — Transmit electrical signals over distances.
Neuronal structure (axon, dendrites) allows rapid signal transmission and connections with many other cells.
Q44. Skeletal muscle fibres are multinucleate because:
Answer: A — They are formed by fusion of many cells during development.
Myoblasts fuse to form long multinucleated muscle fibres, supporting high protein production along their length.
Q45. Which cell type would have abundant rough ER?
Answer: A — Cells producing many secreted proteins (eg. pancreatic cells).
Rough ER is involved in synthesis of proteins to be secreted; secretory cells therefore have extensive RER.
Topic: Practical Skills & Investigative Questions
Q46. Which stain is commonly used to observe nucleus in onion peel cells?
Answer: B — Methylene blue.
Methylene blue stains nucleic acids, making nucleus visible under a light microscope in animal and plant cells.
Q47. To prepare a temporary mount of cheek cells, which of the following is necessary?
Answer: B — Using a wet mount with saline and stain.
A wet mount with saline preserves cells temporarily; a stain (eg. methylene blue) highlights nucleus for observation.
Q48. Which instrument is essential for measuring the magnification of an image in microscope practicals?
Answer: A — Ocular micrometer and stage micrometer.
Calibration with a stage micrometer lets you measure actual sizes using an ocular micrometer scale.
Q49. Which safety precaution is important while using a microscope?
Answer: B — Start with low power objective and focus, then increase magnification.
Low power gives larger field of view and easier focusing; rough handling or sunlight can damage slides or optics.
Q50. During staining, which of the following will best preserve cellular structure for observation?
Answer: B — Fixation followed by appropriate staining.
Fixation preserves cellular structures and prevents decay; staining then enhances contrast for observation.
All MCQs are aligned with NCERT Class 9 Biology — Chapter 5: The Fundamental Unit of Life. Use these for practice, revision, and board exam preparation.