There are some sacs, cavities or tubules which form a network by themselves are known as the endoplasmic reticulum.
Discovery: In 1945 Porter along with his associates first discovered endoplasmic reticulum.
Structure: They are surrounded by a single membrane.
(a) They are of two types according to the presence of ribosome:
- Smooth endoplasmic reticulum: Ribosomes are absent in this type of endoplasmic reticulum.
- Rough endoplasmic reticulum: Ribosomes are present in the endoplasmic reticulum.
(b) They are of three types on the basis of shape:
- Cystemae: They are long, un-branched and are arranged parallely.
- Vesicle: They are round and OVA shaped and are distributed scatteredly.
- Tubules: Tubular and branched
(i) It helps in the formation of the cytoplasmic framework and mechanical activities.
(ii) It helps in the formation of cell organelles
(iii) Conduction of enzyme, protein and lipid and their proper distribution
(iv) Helps in protein and lipid synthesis.