What is Endoplasmic reticulum, its structure, types, occurrence and Function????

 Endoplasmic reticulum is a cell organelle. All the description on it are given below in brief:-



Fig:-Structure of E.R. 

#Endoplasmic Reticulum(ER). 

-->Endoplasmic reticulum is tubular, 

 canal like structure found in the

 cytoplasm of both animal cells & plant

 cells. It contains ribose sugar and 

 connected with the cell membrane to the 

nuclear membrane of the nucleus.Though 

ER was first observed by Garnier (1897 A.D.)

 but its ultrastructure was first given by 

Porter, Claude, and Fullam (1945 A.D.). The

 term "Endoplasmic Reticulum" was given 

by Porter (1953 A.D.).

#Occurrence.

-->The endoplasmic reticulum is present in 

all the eukaryotic cells except germinal

 cells and matured mammalian R.B.C. It is 

also absent in prokaryotes. The occurrence 

and development of ER depends upon the 

metabolic state and stage of differentiation 

of cells e.g.absent in embryonic cells, less 

developed in spermatocytes (only a few 

vesicles) and well developed in fully 

differentiated and metabolically active 

cells. (e.g, cells of pancreas, liver, etc.).

*Morphologically, the Endoplasmic

 Reticulum is composed of three kinds

 of structure and they are: -



Fig:-parts of E.R. 

1)Cisternae:- The cisternae are long 

flattened sac like unbranched tubules 

having diameter 40 to 50 nm. They are 

arranged parallel in bundles.

2)Vesicles:-The vesicles are oval structure

 having diameter 25 to 500 nm. They often 

remain scattered in the cytoplasm and 

occur in most cells but especially abundant 

in the pancreatic cells. 

3)Tubules:-The branched like structure 

forming the reticular system along with 

Cisternae and Vesicles. They usually have 

diameter from 50 to 190 nm.

*According to presence of ribosome on it's 

surface, it is classified into two types.

Fig:-Smooth E.R.

1) Smooth endoplasmic reticulum :-

 

The types of reticulum which possess 

smooth surface because the ribosome are 

not attached with it's surface. so, it is also 

known as agranular Endoplasmic 

Reticulum. It is found in those cells which 

cannot take part in protein synthesis.

Fig:-Rough E.R.

2)Rough Endoplasmic Reticulum(R.E.R.):-

The types of reticulum which possess rough 

surface because the ribosome are attached 

with it's surface. so, it is also known as 

Granular Endoplasmic Reticulum. 

Ribosome play a vital role in protein

synthesis. 

So, it is found in those cells which takes 

Part in protein synthesis.

#Differences between Smooth Endoplasmic Reticulum and Rough Endoplasmic Reticulum. 

• Smooth Endoplasmic Reticulum

1) It possess smooth surface.

2)Ribosome are not attached with it.

3)It do not take part in protein syntheses

• Rough Endoplasmic Reticulum

1)It possess rough surface. Fu

2)Ribosome are attached with it.

3) It take part in protein synthesis.

#Functions of Endoplasmic reticulum. 

1)During cell division, it accumulate around

 the chromosome group & fuse to form 

nuclear membrane.

2)It's main function is to import and export 

and intracellular transportation of various 

substance to different parts of the cell. 

3) It indirectly takes part in protein

synthesis because ribosome are attached 

with it.

4)It helps in transportation of proteins..

5) It plays role in the formation of cell plate 

during cytokinesis in plant cells. 

6)It also helps in synthesis of lipids and 

glycogen.

7) It protects the Nucleus ( Brain of cell)

from mechanical injury and hence it is also 

known as "endoskeleton of the cell".