Cell


 
 
Concept Explanation
 

Cell

There is large variety of living organisms around us. Each organism starts its life as a single cell. Cells have many functions which keep an organism alive. The cells is the basic structural and functional unit of all living organisms. It is the smallest unit of life and thus it is known as building blocks or basic structural unit of life. Every cell have a limited life span. Old and weak cells in the body continually die and are replaced by new cells.

Every organ in our body - the skin, the brain, the muscle or even the bone - is composed of hundreds of thousands of such cells. Similarly, every part of a plant - the leaf, the flower, the root and even the wood - is composed of an exceedingly large number of cells.As the blocks can be joined in many ways to make the building of different shapes and sizes. In the same way all , living organisms are made differently of different shapes, sizes and by different number of cells.

                                                        

Cells are so small that they cannot be seen with naked eyes. So to see a cell we use a device called as microscope.

Microscope: An instrument used to see cells. Simple microscope helps to see small things but not microscopic objects. As cells are microscopic structures, are only visible under a powerful microscope like a compound microscope.

Every cell have a limited life span. Old and weak cells in the body continually die and are replaced by new cells.

The life span of different cells of the body vary differently as shown in the table.                       

                            Cell Type                 Life  Span
  Red blood cells     less than 120 days
  White blood cells      13 to 20 days
  Liver cell     200 to 300 days
 Skin epidermal cells      2 to 4 weeks
 Cardiac cell      Long lived
 Nerve cell       Long lived
 Epithelia of small intestine     1 week or less

 

 

 

 

 

 

   

    

 

Sample Questions
(More Questions for each concept available in Login)
Question : 1

Temporary mount of a tissue is made in ______________________.

Right Option : C
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Question : 2

Match the following

Column AColumn B
(1) liver cells(A) 20 days
(2)White blood cells(B) 120 days
(3) Skin cells(C) 14 days
(4) Red blood cells(D) 300-500 days
Right Option : B
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Explanation
Question : 3

Human cheek cells are commonly stained with ________________.

Right Option : A
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Explanation
 
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