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Cell : The Unit of Life

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New cells generate from
  • bacterial fermentation
  • regeneration of old cells.
  •  pre-existing cells.
  • abiotic materials.


Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles ? State their function and draw labelled diagrams of both.

 Chloroplasts and mitochondria are organelles which have double membrane . 

Mitochondria - is called the power house of the cell as it produces cellular energy in the form of ATP. It is bounded by two membrane, the inner membrane forms inner foldings called cristae. The matrix has a single circular DNA molecule. 

Chloroplasts - are also double membrane bound organelles which help to trap the solar energy and produce food. The stroma contains many flattened disc like structures called thylakoids which are arranged in stacks to gorm grana. The chloroplasts consists of the pigment chlorophyll that helps to convert sun's energy to chemical energy. 

Functions of :

Mitochondria - It produces the cellular energy in the form of ATP.

Chloroplasts - trap the energy of the sun and produce food.


 Match the following
A.  Cristae (i) Flat membranous sacs in stroma
B. Cisternae (ii)  Infoldings in mitochondria
C. Thylakoids (iii) Disc-shaped sacs in Golgi apparatus.




 Infoldings in mitochondria




Disc-shaped sacs in Golgi apparatus.




Flat membranous sacs in stroma

Which of the following is not correct?
  •  Robert Brown discovered the cell.
  • Schleiden and Schwann formulated the cell theory.
  • Virchow explained that cells are formed from pre-existing cells.
  • A unicellular organism carries out its life activities within a single cell.


 Which of the following is correct :
  • Cells of all living organisms have a nucleus.
  • Both animal and plant cells have a well defined cell wall.
  •  In prokaryotes there are no membrane bound organelles.
  •  Cells are formed by de novo from abiotic materials.