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Tuesday, August 21, 2012

8th The Fundamental Unit of Life : The Cell Summative assessment VIII Biology

Answer the following questions in detail

1. Who discovered cell? 

Ans: Robert Hooke (1665)

Questions: 2. How do CO2 and water move in and out of the cell ? 

Ans: CO2 by the process of diffusion and water by Osmosis

Detail: Due to accumulation of CO2 inside the cell, the concentration of CO2 in the cell increases as compared to the concentration outside the cell. Because of this CO2 from inside of the cell diffuses out. In the same way due to increasing concentration of O2 outside the cell, O2 diffuses in the cell. 

when the concentration of water around the cell is more than that in the cell, then water enters into the cell through osmosis. Such type of solution is known as hypotonic solution. As water enters, the cell swells up.

when the concentration of water outside the cell is less than inside the cell, then water moves out of the cell by the process of osmosis. Such type of solution is known as hypertonic solution. Due to the phenomenon cell shrinks. This is known as plasmolysis.

3. Why plasma membrane is called a selectively permeable membrane? 


Ans: It allows only selected substance to enter or leave the cells.

4. Why lysosomes is known as suicide bag ? 

Ans: During disturbance in cellular metabolism destruction of cells take place. The lysosomes enzymes come out and destroy the cell by digesting all the organelles of the cell. Thus lysosomes is known as “Suicidal bags” of the cell.

Questions: 5. Which organelle is known as power house of the cell ? and why ? 

Ans: Mitochondria. In mitochondria, cellular respiration takes place and release energy and ATP hence it is known as “Power House” of the cell.

Questions: 6. What is osmosis ?

Ans: The process by which the molecules of solute move from lower concentration to higher concentration.. Water enters into the cell through osmosis

Questions: 7. What is Plasmolysis?

Ans: water moves out of the cell by the process of osmosis cell shrinks. This is known as plasmolysis.

Questions: 8. State two main functions of cell wall. 

Ans: (a) It maintains the shape of the cell. (b) it protects the cells from water absorption away from the cell wall. This phenomenon is called plasmolysis.

8th The Fundamental Unit of Life : The Cell Formative assessment MCQ

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IX The Cell & Fundamental Unit of life -MCQ Unsolved
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