Topic outline

    • Cell Structure and Functions

      Q44. What is protoplasm?

      Ans. The entire content of a living cell is known as protoplasm. It includes the cytoplasm and the nucleus. Protoplasm is called the living substance of the cell.


      Q45. What are multicellular organisms? Give two examples.

      Ans. Organisms made of more than one cell are called multicellular (multi: many; cellular: cell) organisms. Most of the plants and animals around us are multicellular organisms. Example: a mango tree, a deer, etc.

      Q46. Why are plant and animal specimens usually stained with dyes before observing them through a microscope? Name one stain used for this purpose.

      Ans. Stains (dyes) are used to colour parts of the cell to study the detailed structure. Methylene blue solution stain is used in the study of structure of cell.


      Q47. Which part of the cell contains organelles?

      Ans. Cytoplasm is a part of the cell that contains organelles such as mitochondria, golgi bodies, ribosomes, etc. It is the jelly-like substance present between the cell membrane and the nucleus.


      Q48. Where are chromosomes found in a cell? State their function.

      Ans. Nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring.


      Q49. What is nuclear membrane? State its function.

      Ans. Nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. This membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus.

      Q50. What are the different shapes of cells?

      Ans. Generally, cells are round, spherical or elongated. Some cells are long and pointed at both ends. They exhibit spindle shape. Cells sometimes are quite long. Some are branched like the nerve cell or a neuron.


      Q51. Are the cells in an elephant larger than the cells in a rat?

      Ans. The size of the cells has no relation with the size of the body of the animal or plant. It is not necessary that the cells in the elephant be much bigger than those in a rat. The size of the cell is related to its function.


      Q52. Explain why chloroplasts are found only in plant cells?

      Ans. Green coloured plastids are called chloroplasts. They provide green colour to the leaves. Chlorophyll in the chloroplasts of leaves is essential for photosynthesis. As only plants can perform photosynthesis, so chloroplasts are found only in plant cells.


      Q53. What is the difference between amoeba and white blood cell?

      Ans. The difference between amoeba and white blood cell is that while amoeba cell is a full-fledged organism capable of independent existence, white blood cell is merely a cell of human blood which is not a full-fledged organism and hence cannot exist independently.

      Q54. Which part of the cell gives it shape?

      Ans. Components of the cell are enclosed in a membrane. This membrane provides shape to the cells of plants and animals. Cell wall is an additional covering over the cell membrane in plant cells. It gives shape and rigidity to these cells. Bacterial cell also has a cell wall.


      Q55. ‘Cells are the basic structural units of living organisms’. Explain.

      Ans. Both, bricks in a building and cells in the living organisms, are basic structural units. The buildings, though built of similar bricks, have different designs, shapes and sizes. Similarly, in the living world, organisms differ from one another but all are made up of cells. Cells in the living organisms are complex living structures unlike non-living bricks.


      Q56. Does the number of cells in an organism affect its functioning? Explain.

      Ans. The number of cells being less in smaller organisms does not, in any way, affect the functioning of the organisms. A single-celled organism performs all the necessary functions that multicellular organisms perform. An organism with billions of cells begins life as a single cell which is the fertilized egg. The fertilised egg cell multiplies and the number of cells increases as development proceeds.


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