Endoplasmic Reticulum

Endoplasmic Reticulum It is a system of highly branching membranes, which almost fills the space inside the cell membrane. Some of the branches of endoplasmic reticulum are connected to the plasma membrane while some of them are connected to the nuclear membrane. An examination of endoplasmic reticulum under the electron microscope reveals two types of membranes:

Endoplasmic Reticulum Smooth endoplasmic reticulum Rough endoplasmic reticulum

in which the surface of the tubules lacks granules Smooth endoplasmic reticulum(SER) in which the surface of the tubules lacks granules

Rough endoplasmic reticulum (RER) in which the surface of the tubules contain numerous granule-like structures called ribosomes

Endoplasmic reticulum is absent in some cells such as embryonic cells and mature red blood corpuscles. Endoplasmic reticulum serves the following functions. • It facilitates the transport of materials inside the cell. • It forms an internal supporting framework for the cell, called cytoskeleton. • It provides surface for the synthesis of a variety of substances in the cell. SER provides surface for the synthesis of lipids while RER provides surface for the synthesis of proteins and carbohydrates. • It provides a pathway for the distribution of nuclear material from one cell to another. • Being highly coiled in nature, it provides an increased surface area for various enzyme catalyzed reactions

Ribosome

1. Unlike most other organelles, ribosomes are not surrounded by a membrane... 2. Some are free in the cytoplasm (Prokaryotes); others line the membranes of rough endoplasmic reticulum (rough ER).