Plastids


 
 
Concept Explanation
 

Plastids

Plastids: Plastids are double-membraned organelles which are found only in plant cells. They are usually spherical or discoidal in shape, and their average size is 4 to 6 p.m. A plastid shows two distinct regions : grana and stroma.  Grana are stacks of membrane-bound, flattened, discoid sacs containing chlorophyll molecules. These molecules are responsible for the production of food by the process of photosynthesis. They are, therefore, called the kitchen of the cell. The homogenous matrix in which grana are embedded is known as stroma. Like mitochondria, plastids also contain their own DNA and ribosomes. Plastids are of three types:

  • Chloroplasts contain the green pigment chlorophyll, which helps plants in making food by using sunlight by the process of photosynthesis.
  • Chromoplasts contain non-green pigments that give colour to flowers and fruits.
  • Leucoplasts are colourless and store food in the form of carbohydrates, fats, and proteins.
  • Functions of Plastids

  • By trapping solar energy, green plastids manufacture food through photosynthesis.
  • Chromoplasts provide colour to various flowering parts.
  • Leucoplasts help in the storage of protein, starch and lipid (oil)
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    Sample Questions
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    Question : 1

    Chlorophyll pigments are present in  _____________________

    Right Option : B
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    Explanation
    Question : 2

    Besides nucleus,DNA is also found in __________________

    Right Option : B
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    Explanation
    Question : 3

    _______________ is a component of chlorophyll.

    Right Option : C
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    Explanation
     
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