What is endoplasmic reticulum? Give its types and functions.

Endoplasmic reticulum is an interconnected system of membrane lined channels distributed extensively throughout the cytoplasm. At one end ER is connected to the outer membrane of the nucleus and at the other end to the plasma membrane. It occurs in three forms:

• Cisternae: These are parallel interconnected flattened sac-like structures.

• Tubules: Often branched, network-like structures

• Vesicles: These are round or oval shaped structures.

Endoplasmic reticulum is of two types:

(a) Rough endoplasmic reticulum: Ribosomes are attached on its surface for protein synthesis.

(b) Smooth endoplasmic reticulum: It is not associated with ribosomes.

Functions: (i) It forms supporting skeletal framework of the cell.

(ii) Endoplasmic reticulum serves as channels and helps in transporting the different materials like proteins between various regions in the cytoplasm as well as between the nucleus and the cytoplasm.

(iii) It also provides a large surface area inside the cells for various chemical activities.

(iv) SER plays a crucial role in detoxifying many poisons and drugs.