12 Structural Difference Between Smooth And Rough Endoplasmic Reticulum

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Endoplasmic Reticulum (ER)

Endoplasmic reticulum (ER) is a large organelle found in both eukaryotic animal and plant cells. It is made up of membraneous sheets and tubules that begin near the nucleus and extend across the cell. The Endoplasmic reticulum creates, packages and secretes many of the products created by a cell. The endoplasmic reticulum is not found in red blood cells and spermatozoa. Endoplasmic reticulum is made up of two subunits that can be differentiated from one another based on their appearance and function. The two subunits are:

  • Rough endoplasmic reticulum
  • Smooth endoplasmic reticulum.

The two types of endoplasmic reticulum often appear as if separate, but are sub-components of the same organelle. The two ERs share many of the same proteins and engage in certain common activities such as the synthesis of certain lipids and cholesterol. Different types of cells contain different ratios of the two types of ER depending on the activities of the cell. Rough endoplasmic reticulum is involved in protein synthesis, protein folding, protein quality control and dispatch whereas, smooth endoplasmic reticulum is associated with the production and metabolism of fats and steroid hormones.

The smooth endoplasmic reticulum is distinguished from the other parts of the endoplasmic reticulum by the absence of membrane-bound ribosomes. This organelle is also morphologically distinct, often made of tubular structures referred to as cistarnae. Smooth ER is prominent in cells of the liver that process harmful chemicals, in cells of the endocrine system such as those in the adrenals that produce steroid hormones and in excitable cells such as neurons and muscle cells that use calcium ion signaling.

The Rough Endoplasmic Reticulum is characterized by the presence of membrane-bound ribosomes that give it a distinctive appearance under the microscope. These ribosomes look like studs and distinguish the organelle from the smooth sections of the ER. Some proteins are also synthesized by strings of ribosomes, called polysomes. The rough ER can be identified by it’s morphology as well, it often consists of convoluted, flattened sac-like structures that originate near the nucleus. The lumen of the rough ER is continous with perinuclear space and the membranes of the rough ER are associated with the outer nuclear membrane.

In many cases, cells specializing in the production of proteins will tend to have a larger amount of rough endoplasmic reticulum while cells producing lipids and steroid hormones will have a greater number of smooth endoplasmic reticulum.

Facts About Rough Endoplasmic Reticulum

  • Rough Endoplasmic Reticulum have ribosomes on the outer surface of its membrane, a factor that gives them a granular appearance.
  • Rough endoplasmic reticulum are located near the nuclear membrane
  • Rough endoplasmic reticulum are located near the nuclear membrane
  • Rough endoplasmic reticulum plays a role in the formation of cis-face of Golgi body
  • Rough endoplasmic reticulum have small pores below attached to ribosomes  for passage of synthesized  polypeptides into Endoplasmic Reticulum (ER) channels.
  • Rough endoplasmic reticulum do not have enzymes
  • Rough Endoplasmic  reticulum  are found  more in number in cells which have vast protein metabolism
  • The main function of rough endoplasmic reticulum is synthesis and storage of proteins
  • Rough endoplasmic reticulum contains Ribophorins for providing attachment to ribosomes. 
  • Rough endoplasmic reticulum originates from the nuclear envelope
  • Rough endoplasmic reticulum provides bio-chemicals for Golgi apparatus.
  • Rough endoplasmic reticulum is mainly formed of three-dimentional polygonal networks of tubules known as cisternae.

Facts About Smooth Endoplasmic Reticulum

  • Smooth Endoplasmic Reticulum do not have ribosomes attached to the outer membrane and thus have a smooth appearance.
  • The smooth endoplasmic reticulum are located near the plasma membrane.
  • The smooth endoplasmic reticulum are located near the plasma membrane.
  • Smooth endoplasmic reticulum plays a role in the formation of lysosomes.
  • Smooth endoplasmic reticulum do not have pores so materials synthesized in it cannot pass through it.
  • Smooth endoplasmic reticulum has enzymes for detoxification.
  • smooth endoplasmic reticulum  are more in number in the cells which have vast lipids or steroid metabolism.
  • The main function of smooth endoplasmic reticulum is synthesis and storage of lipids, steroids and glycogen.
  • Ribophorins are absent in smooth endoplasmic reticulum.
  • Smooth endoplasmic reticulum originates from rough endoplasmic reticulum when it sheds off its ribosomes.
  • Smooth endoplasmic reticulum provides vesicles for cis-face of Golgi apparatus.
  • Smooth endoplasmic reticulum is formed of vesicles and tubules.

Differences Between Rough Endoplasmic Reticulum and Smooth Endoplasmic In Tabular Form

Basis of Comparison  Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum
Key Difference Have ribosomes on the outer surface of its membrane, a factor that gives them a granular appearance They do not have ribosomes attached to the outer membrane and thus have a smooth appearance.
Location They are located near the nuclear membrane. They are located near the plasma membrane.  
Role Plays a role in the formation of cis-face of Golgi body. Plays a role in the formation of lysosomes.
Structure They have small pores below attached to ribosomes for passage of synthesized polypeptides into Endoplasmic Reticulum (ER) channels. They do not have pores so materials synthesized in it cannot pass through it.
Enzymes Enzymes are Absent. They have enzymes for detoxification.  
Presence They are found more in number in cells which have vast protein metabolism. They are more in number in the cells which have vast lipids or steroid metabolism.  
Ribophorins They contain Ribophorins for providing attachment to ribosomes Ribophorins are absent.
Main Function  Synthesis and storage of proteins. Synthesis and storage of lipids, steroids and glycogen.
Origin Originates from the nuclear envelope. Originates from rough endoplasmic reticulum when it sheds off its ribosomes.  
Other Function Provides bio-chemicals for Golgi apparatus. Provides vesicles for cis-face of Golgi apparatus.
Formation Mainly formed of polygonal networks of tubules called cisternae. Mainly formed of vesicles and tubules.

Summary

  • Smooth endoplasmic reticulum is associated with the production and metabolism of fats and steroid hormones. It also plays a role in the detoxification of harmful metabolic byproducts. The smooth endoplasmic reticulum is distinguished from other parts of the endoplasmic reticulum by the absence of membrane-bound ribosomes.
  • Smooth Endoplasmic Reticulum is primarily composed of vesicles and tubules.
  • Rough endoplasmic reticulum is an organelle found in eukaryotic cells. Its main function is to produce proteins. It is primarily composed of three-dimentional polygonal networks of tubules called cisternae. The cisternae are made up of flattened membrane disks, which are involved in modification of proteins.
  • The reason rough endoplasmic reticulum is called ‘rough’ is because of the ribosomes that cover its surface and make it appear bumpy under microscopic magnification.

5 COMMENTS

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  2. In our group work we intensely argued about the exact role of Enzymes in smooth Endoplasmic reticulum, Wooh, thanks to this article, it has helped me to settle the whole doubt..

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