Endoplasmic Reticulum

Endoplasmic reticulum is a network of membranes or tubes in a cell through which materials move. As an organelle in a eukaryotic cell (complex cells having nuclei and other organelles), it is involved with the production of new proteins as well as with the movement of materials throughout the cell.

The name endoplasmic reticulum means "an inside formed network," and these words properly describe this network of connected folds, tubes, and sacs that are found in all eukaryotic cells (those with a distinct nucleus). As an organelle in a cell, the endoplasmic reticulum is a specialized structure and has certain tasks to perform. The endoplasmic reticulum has been described as the pipeline or conveyer belt through which supplies are moved about the factory (or the cell). Viewed through a microscope, the endoplasmic reticulum looks like flat, tubular membranes that are connected to the nucleus and which spread throughout the interior of the cell. There are two types of endoplasmic reticulum: rough endoplasmic reticulum and smooth endoplasmic reticulum. Rough endoplasmic reticulum appears to have a pockmarked, or rough outer surface, and this is because it is covered with ribosomes, which are structures in the cell that make proteins. Smooth endoplasmic reticulum has no ribosomes dotting its surface. Smooth endoplasmic reticulum has the job of packaging and distributing materials needed for making proteins and other substances, and also is responsible for "detoxifying" any substance in the cell that might be poisonous. Both types of endoplasmic reticulum are essential to the cell if it is to be able to move materials around to where they are needed. There is always a large amount of endoplasmic reticulum within a cell, and in many cells it takes up nearly half the amount of interior space. Although both are involved with transport, smooth endoplasmic reticulum curves around the cell's cytoplasm (its jelly-like fluid) like interconnecting pipelines, while rough endoplasmic reticulum looks more like stacked and flattened sacs. Both smooth and rough endoplasmic reticulum are connected directly to many other organelles in the cell, and without the membrane pipeline that the endoplasmic reticulum provides, eukaryotic cells would not be able to carry out many of their functions.

[See alsoCell; Organelle ]