Home Preparation for National Talent Search Examination (NTSE)/ Olympiad
Chapter : 1. The cell
Types of Endoplasmic Reticulum
The Endoplasmic Reticulum (ER) is of two types • Rough endoplasmic reticulum (RER) • Smooth endoplasmic reticulum (SER) • Rough Endoplasmic reticulum (RER). These appear rough under a microscope because of the presence of a large number of grain-like ribosomes over their cytoplasmic surface. The ribosomes are the sites of protein synthesis. Thus, RER is engaged in the synthesis and transport of proteins. Generally, RER is more abundant in the deeper part of cytoplasm near the nucleus where it is connected with the outer membrane of the nuclear envelope. RER is well developed in the cells that synthesize and secrete proteins. • Smooth Endoplasmic Reticulum (SER). It consists mainly of tubules and vesicles. It is free of ribosomes and is more abundant near the peripheral part of the cytoplasm where it may be attached to the plasma membrane. The SER helps in the synthesis of fat or lipid molecules. It is, therefore, well developed in the cells that secrete lipids.