Biology class 9th Fundamental unit of life cell Part - 5

             📚Biology 📚

                      Class - 9th📝

             Chapter - 1📝

  Fundamental Unit Of Life

         👉  Part - 5🏝️

     ExamDeepLearning


 CELL ORGANELLES


  #  On the basis of number of membranous covering, cell organelles are of three types : 


  1. Double membrane bound (mitochondria and plastids).


  1. Single membrane bound (endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles).


  1. Membraneless organelles (ribosome and centrosome).


    #  ENDOPLASMIC RETICULUM


  • Endoplasmic reticulum was discovered by a porter.


  • It is a large network of single membrane bound tubules and sheets present in the cytoplasm.


  • The endoplasmic reticulum membrane is similar in the structure of plasma membrane.


  • When observed under a microscope, it appears in three forms - tubules, cisternae and vesicles.


  • One end of the endoplasmic reticulum is connected to the outer membrane of the nucleus and the other end is connected to the plasma membrane.


  • Endoplasmic reticulum is absent in prokaryotes.


     # Types of endoplasmic reticulum 


  • Depending upon the presence or absence of ribosomes.


  • Endoplasmic reticulum is of two types :


  • Rough endoplasmic reticulum (RER)


  • Smooth endoplasmic reticulum (SER)


  1. ROUGH ENDOPLASMIC RETICULUM (RER)


  • Endoplasmic reticulum with a ribosome attached on its surface for synthesizing proteins is called Rough endoplasmic reticulum.


  • It is present in all active Cells.


  • The Rough endoplasmic reticulum appears rough under microscope due to the presence of ribosomes on its surface.


     2.  Smooth endoplasmic reticulum


  • Endoplasmic reticulum that does not contain a ribosome on its surface is called smooth endoplasmic reticulum.


  • It helps in the synthesis of cats or lipids, glycogen etc.


  • Smooth endoplasmic reticulum appears smooth under the microscope due to the absence of ribosomes on its surface.


     # FUNCTIONS OF ENDOPLASMIC RETICULUM :


  1. Endoplasmic reticulum serves as a channel for the transport of material (proteins) between various regions of the cytoplasm.


  1. Endoplasmic reticulum functions as a cytoplasmic framework providing surface for some of the biochemical activities of the cell.


  1. Rough endoplasmic reticulum is concerned with the synthesis and transport of proteins in the cell.


  1. Smooth endoplasmic reticulum is involved in the process of detoxification of many poisons and drugs in liver cells.


  1. Smooth endoplasmic reticulum plays an important role in the biosynthesis of cholesterol (lipid).


  1. Smooth endoplasmic reticulum synthesizes steroid hormones such as estrogen, testosterone and cortisol.


  1. Lipids from smooth endoplasmic reticulum and some proteins from rough endoplasmic reticulum help in building of the cell membrane. This process is known as membrane biogenesis.



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