Endoplasmic reticulum is a tubular sac like cellular organelles enclosed by a continuous single layered membrane and situated just after the nucleus in most of the prokaryotic cells. It has many different functions but played a very important role in protein sorting.
LOCATION: It’s generally present in most of the eukaryotic cells including plant cells. It is located associating with the nuclear membrane.
- The entire endoplasmic-reticulum is covered by a continuous single layered membrane.
- It is the largest organelle in most of the eukaryotic cell. It occupied almost 10% of the total cell volume.
TYPES: There are two types of ER- Rough endoplasmic reticulum (RER) and Smooth endoplasmic reticulum (SER).
Rough ER: In this type of ER is covered by ribosomes associated on the outer surface. These are mainly consisting with cisternae.
Smooth ER: the ER which does not associate with ribosomes on their surface. This ER mainly consisting with the tubules and vesicles.
TYPICAL ULTRASTRUCTURE OF ER: ER is tubular sac like organelle in appearance. It is covered by a single layered membrane consisting of lipid and protein. It contains some special structures. These are mainly three types- 1. Cisternae, 2. Tubules and 3. Vesicles. Inside the cell a fluid filled mosaic area is present known as the endoplasmic matrix.
FUNCTION: The main function of ER is protein processing and sorting. But it has many other roles.
- The ribosomes present on the surface of RER play a vital role in protein synthesis.
- It acts as the storage organ for some cellular material and transport them through the tubules.
- The SER present in the liver cells help to destroy the toxicity of toxins and some drugs.
- Some enzymes, present in the ER play a vital role in digestion.
NOTABLE: Endoplasmic Reticulum, present in the cytoplasm of the muscle cell, known as sarcoplasmic reticulum. In the cells of scrotum and adrenal cortex a huge number of SER is present.
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