The Fundamental Unit of Life (Class-9 Biology) Important Questions and answers

Question and Answer

1. Who discovered the first cell under microscope?

Show Answer Robert Hooke in 1665.

2. Name the scientist who discovered the first living cell?

Show Answer Anton van Leeuwenhoek.

3. What is the meaning of the word cell that is derived from Latin?

Show Answer The word 'cell' comes from the Latin word "cella," meaning small room.

4. What is the source for the cork that was used by Robert Hooke?

Show Answer The cork came from the bark of the cork oak tree.

5. What is cell theory? Name the scientist who proposed it.

Show Answer Cell theory was proposed by Matthias Schleiden and Theodor Schwann, stating that all living organisms are composed of cells.

6. How did Rudolf Virchow modify the cell theory that was given by Schleiden and Schwann?

Show Answer Rudolf Virchow added that "All cells arise from pre-existing cells," thus modifying the cell theory.

7. State the contribution of Robert Brown in the discovery of a cell component.

Show Answer Robert Brown discovered the nucleus in plant cells.

8. Differentiate between unicellular and multicellular organisms. Provide examples for each.

Show Answer Unicellular organisms are composed of one cell (e.g., bacteria, amoeba). Multicellular organisms are composed of multiple cells (e.g., humans, plants).

9. Why do cells have a particular shape and size?

Show Answer Cells have a particular shape and size due to their function and the requirements of the organism.

10. What do you mean by the division of labour inside a cell?

Show Answer Division of labor means that different cell organelles perform specific tasks for the cell to function efficiently.

11. What is protoplasm?

Show Answer Protoplasm is the living substance inside the cell, consisting of the cytoplasm, nucleus, and cell membrane.

12. Who coined the term protoplasm?

Show Answer The term "protoplasm" was coined by the scientist Johannes Purkinje in 1840.

13. What is the role of plasma membrane in a cell?

Show Answer The plasma membrane regulates the entry and exit of substances, protecting and supporting the cell.

14. Why is the plasma membrane referred to as selectively permeable?

Show Answer The plasma membrane is selectively permeable because it allows only specific substances to pass through while blocking others.

15. Explain how the exchange of O2 and CO2 takes place in a cell.

Show Answer The exchange of O2 and CO2 occurs through diffusion across the plasma membrane, from areas of higher concentration to lower concentration.

16. Define osmosis.

Show Answer Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration through a semipermeable membrane.

17. What do you understand by hypotonic, hypertonic, and isotonic solution? Also mention what will happen to a cell that is placed in these solutions.

Show Answer - Hypotonic solution: Lower solute concentration outside the cell. The cell swells as water enters. - Hypertonic solution: Higher solute concentration outside the cell. The cell shrinks as water exits. - Isotonic solution: Equal solute concentration inside and outside the cell. No change in cell size.

18. How do plant cells gain water?

Show Answer Plant cells gain water through osmosis, where water moves from the surrounding soil into the root cells.

19. State the composition of plasma membrane.

Show Answer The plasma membrane is primarily composed of a phospholipid bilayer, proteins, cholesterol, and carbohydrates.

20. How can you observe the plasma membrane?

Show Answer The plasma membrane can be observed using electron microscopes due to its thin structure.

21. Define endocytosis and exocytosis. Give examples of endocytosis.

Show Answer Endocytosis is the process by which cells engulf materials from outside. Example: Phagocytosis, where cells engulf particles. Exocytosis is the process by which cells expel materials to the outside.

22. State the role of the cell wall in plants. Also provide its major component.

Show Answer The cell wall provides structural support and protection. Its major component is cellulose.

23. Define plasmolysis.

Show Answer Plasmolysis is the process where the cell membrane pulls away from the cell wall due to water loss when the cell is in a hypertonic solution.

24. State the reason as to why the plant cell can withstand a hypotonic solution for a long time without bursting.

Show Answer The plant cell has a rigid cell wall that prevents it from bursting, even when it takes in excess water in a hypotonic solution.

25. Name at least two different stains that could be used to colour the cells for observing under a microscope.

Show Answer Two commonly used stains are methylene blue and iodine solution.

26. The nucleus is surrounded by how many membranes? Also mention its role.

Show Answer The nucleus is surrounded by a double membrane known as the nuclear envelope. It regulates the exchange of materials between the nucleus and the cytoplasm and protects the genetic material.

27. State the composition of chromatin.

Show Answer Chromatin is composed of DNA and proteins, primarily histones, which help in the packaging of DNA.

28. Provide the full form of DNA and RNA.

Show Answer DNA stands for Deoxyribonucleic Acid, and RNA stands for Ribonucleic Acid.

29. Define Gene.

Show Answer A gene is a segment of DNA that contains the instructions for making a specific protein, which determines traits and functions in an organism.

30. When can you see chromatin in a cell?

Show Answer Chromatin is visible in the cell during the interphase when the cell is not dividing. It condenses into chromosomes during cell division.

31. State the function of the nucleus.

Show Answer The nucleus controls the cell's activities, including growth, metabolism, and reproduction, by regulating gene expression.

32. Differentiate between prokaryotic and eukaryotic cells. Also, provide examples for both.

Show Answer Prokaryotic cells lack a nucleus and membrane-bound organelles. Example: Bacteria. Eukaryotic cells have a nucleus and membrane-bound organelles. Example: Animal and plant cells.

33. How are the chlorophyll present in the case of prokaryotic cells?

Show Answer In prokaryotic cells, chlorophyll is found in the cytoplasm or specialized membranes, as they lack chloroplasts.

34. State the role of cytoplasm in a cell.

Show Answer The cytoplasm provides a medium for chemical reactions to occur and houses the cell organelles, allowing them to function efficiently.

35. What are the two types of ER? Mention their role in detail.

Show Answer The two types of Endoplasmic Reticulum (ER) are: - Rough ER: Involved in protein synthesis and transport. - Smooth ER: Involved in lipid synthesis, detoxification, and calcium storage.

36. What do you understand by membrane biogenesis?

Show Answer Membrane biogenesis refers to the process by which new membranes are created in the cell, particularly the formation of the lipid bilayer and membrane proteins.

37. Name the organelle involved in detoxification of drugs and poisons.

Show Answer The smooth Endoplasmic Reticulum (Smooth ER) is involved in detoxification of drugs and poisons.

38. State the structural composition of the Golgi Apparatus.

Show Answer The Golgi apparatus consists of a series of flattened, membrane-bound sacs called cisternae, which are stacked together.

39. Name the scientist who discovered Golgi apparatus.

Show Answer The Golgi apparatus was discovered by Camillo Golgi in 1898.

40. List out any four roles of Golgi bodies.

Show Answer Four roles of Golgi bodies are: - Modifying and packaging proteins. - Transporting lipids. - Producing lysosomes. - Secretion of cellular materials.

41. Why are lysosomes referred to as scavengers of the cell?

Show Answer Lysosomes are referred to as scavengers because they contain enzymes that break down waste materials and cellular debris, cleaning up the cell.

42. How are the membranes of mitochondria organized?

Show Answer Mitochondria have two membranes: an outer membrane that is smooth and an inner membrane that is folded into cristae, increasing surface area for ATP production.

43. Why are Cisterns present in mitochondria?

Show Answer Cisterns are present in the inner membrane of mitochondria to increase surface area for the enzymes involved in cellular respiration, enhancing energy production.

44. What is the full form of ATP and why is it referred to as the energy currency of the cell?

Show Answer ATP stands for Adenosine Triphosphate. It is called the energy currency of the cell because it stores and transfers energy within cells for various cellular processes.

45. What are the 3 different types of plastids and what role do they have in a cell?

Show Answer The three types of plastids are: - Chloroplasts: Contain chlorophyll for photosynthesis. - Chromoplasts: Contain pigments that provide color to flowers and fruits. - Leucoplasts: Involved in the synthesis and storage of starch, lipids, and proteins.

46. Name the cytoplasmic equivalent found in mitochondria and plastids.

Show Answer The cytoplasmic equivalent found in mitochondria and plastids is the stroma, which is a gel-like substance containing enzymes necessary for various processes.

47. Name two cell organelles that contain DNA other than the nucleus.

Show Answer Two cell organelles that contain DNA other than the nucleus are mitochondria and plastids (like chloroplasts).

48. List out 3 locations within the cell where protein synthesis could occur.

Show Answer Protein synthesis can occur in the following 3 locations: - Ribosomes (on rough ER or free in cytoplasm). - Mitochondria (for mitochondrial proteins). - Chloroplasts (for plastid proteins).

49. Why do plants have large central vacuoles?

Show Answer Plants have large central vacuoles to store water, nutrients, and waste products, and to maintain turgor pressure that helps in maintaining the cell shape.

50. Why do you call the cell the structural and functional unit of life?

Show Answer The cell is called the structural and functional unit of life because all living organisms are made up of cells, and all the essential life processes, like metabolism and growth, occur within cells.

51. A cell having 12 chromosomes undergoes mitotic cell division. What will be the number of chromosomes in the daughter cells?

Show Answer In mitotic division, the chromosome number remains the same. Therefore, each daughter cell will also have 12 chromosomes.

52. Name the cell division type involved in the production of gametes or reproductive cells.

Show Answer The type of cell division involved in the production of gametes is meiosis.

53. In a particular cell division, the number of chromosomes in the mother cell and the daughter cells remains the same. Identify the cell division type.

Show Answer The type of cell division where the chromosome number remains the same in both the mother and daughter cells is mitosis.

54. How many daughter cells are produced at the end of single cell division in mitosis and meiosis?

Show Answer Mitosis produces 2 daughter cells, whereas meiosis produces 4 daughter cells.

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