Endoplasmic Reticulum (ER) is a complex network of tubular membranes present within the cytoplasm of the eukaryotic cell, transpiring either with a smooth surface and therefore called as the smooth endoplasmic reticulum or studded with ribosomes and hence called the rough endoplasmic reticulum which is involved in the transportation of materials. These membranes are continuous, joining with the outer membrane of the nuclear membrane. They occur in almost every type of eukaryotic cell except red blood cells and sperm cells.
Endoplasmic Reticulum: Functions
It has a number of jobs within the cell. Its functions are varied. Be its protein synthesis, folding, transport of cellular materials or transport of various proteins, specifically carrying them to the Golgi apparatus. It makes its presence known in all the mentioned areas.
The rough endoplasmic reticulum is named so because of its appearance. It is a series of connected flattened sacs that have many ribosomes on their outer surface, hence the name. It synthesizes and secretes proteins in the liver, hormones and other substances in the glands. This type of endoplasmic reticulum is especially prominent in certain kinds of cells like hepatocytes where active protein synthesis occurs.
The smooth endoplasmic reticulum, on the other hand, does not have ribosomes instead it is tubular in form and is involved in the synthesis of phospholipids, the main lipids in cell membranes and are very important in the process of metabolism. They also transport the products of the rough endoplasmic reticulum to other cell parts, notably the Golgi apparatus.
Basically, endoplasmic reticulum is the transportation system in the eukaryotic cell and can be simply defined as a membrane network within the cytoplasm of cells involved in the synthesis, modification, and transport of cellular materials.
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