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Class 8 Science Question Answers - Cell - Structure and Functions (Old Syllabus)

Q1: What is Cell? Define its components.

Ans: Cell is the structural unit of living organisms.

Components:

  1. Cytoplasm is a jelly-like substance present between the cell membrane and nucleus.
  2. Nucleus is spherical shaped component located in the centre of the cell. It acts as control centre of activities of cell.
  3. Plasma membrane is a porous membrane surrounding the cytoplasm.

Q2: Define "Why plants need cell wall?"

Ans: Cell wall provides rigidity to plant cell. This provides plant cell protection against the variation of environmental condition like variation in temperature, humidity etc.
Q3: Compare plant and animal cell on basis of cellular components.

Ans: Comparison between plant and animal cell:


Part
Plant Cell
Animal Cell
  1. Cell membrane
  2. Cell wall
  3. Nucleus
  4. Nuclear membrane
  5. Cytoplasm
  6. Plastids
  7. Vacuole
  1. Present
  2. Present
  3. Present
  4. Present
  5. Present
  6. Present
  7. Present, large single
  1. Present
  2. Absent
  3. Present
  4. Present
  5. Present
  6. Absent
  7. Present, small numerous

Q4: "Single cell organisms perform all the function that multicellular organisms perform." Define what functions are these. Also define who perform all these function in multicellular.

Ans: Single-celled organism performs all function that multicellular organisms perform. These functions are capturing and digestion of food, respiration, excretion, growth and reproduction.
In single-celled organism these function are performed by overall cell. However, in muticellular organism each function is performed by specific organ. 

Q. 5. Explain the position and functions of nucleus in a cell.
Ans.
Nucleus is the most important component of the living cell. It is round or spherical in shape and situated in the centre of the cell. Nucleus is separated from cytoplasm by a membrane called nuclear membrane. This membrane is porous and allows the movement of materials between the cytoplasm and inside of the nucleus. There is a small and spherical body in the nucleus. It is called nucleolus. Nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. Nucleus also acts as a control centre of the activities of the cell.
 

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FAQs on Class 8 Science Question Answers - Cell - Structure and Functions (Old Syllabus)

1. What is the structure of a cell?
Ans. A cell has a distinct structure that includes a cell membrane, cytoplasm, and nucleus. The cell membrane acts as a protective barrier, the cytoplasm contains various organelles, and the nucleus houses the genetic material.
2. What are the functions of a cell?
Ans. Cells perform several functions essential for the survival of an organism. These functions include taking in nutrients, converting them into energy, carrying out specific biochemical reactions, reproducing, and maintaining homeostasis.
3. What is the role of the cell membrane?
Ans. The cell membrane serves as a selective barrier, controlling the movement of substances in and out of the cell. It also helps maintain the cell's shape, protects the internal contents, and facilitates cell-cell communication.
4. What are organelles?
Ans. Organelles are specialized structures within a cell that perform specific functions. Examples of organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes.
5. How does the nucleus contribute to cell function?
Ans. The nucleus is the control center of the cell and contains the genetic material (DNA). It regulates the cell's activities by directing the synthesis of proteins and coordinating cell growth, division, and reproduction.
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