Endoplasmic reticulum

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Name :- Endoplasmic Reticulum (ER)

Properties :
  • ER is a network of tubular and microsomal vesicular structures which is present inside the cell.
  • The tubules and vesicles are interconnected.
  • ER covered by a limiting membrane which is formed by proteins and bilayered lipids.
  • The lumen (diameter - 400 to 700 angstrom) of ER contains a fluid medium called endoplasmic matrix.
  • Total surface area of ER (in some cells like liver cells) can be as much as 30-40 times the cell membrane area.
  • ER forms the link between nucleus and cell membrane by connecting them.

Endoplasmic Reticulum (ER)


Types of ER ....
  1. Rough Endoplasmic Reticulum (RER) / Granular Endoplasmic Reticulum (GER)
  2. Smooth Endoplasmic Reticulum (SER) / Agranular Endoplasmic Reticulum (AER) / Tubular Endoplasmic Reticulum (TER)
1. RER : Rough appearance of ER is due the attachment of ribosomes (granules) to it's outer surface. Hence, it is also celled GER.

Functions :
  •  Synthesis of proteins (specially those proteins which are secreted from the cells like insulin from β - cells, and formation of glycosylated proteins or glycoproteins by adition of carbohydrate with proteins).
  • Degradation of worn-out organelles like mitochondria by autophagosome.
2. SER : ER with smooth appearance. It is formed by many interconnected tubules.

Functions : 
  • Synthesis of non-protein substances like cholesterol, steroid hormones, lipids, phospholipids, lipoprotein and sebum etc.
  • Role in cellular metabolism by it's enzymes which are present outer surface of the ER.
  • Storage and metabolism of calcium.
  • Catabolism and detoxification of toxic substances some drugs and carcinogens (cancer producing substances) in liver.
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