Part of the endoplasmic reticulum has no attached
ribosomes. This part is called the agranular, or smooth, endoplasmic reticulum.The agranular
reticulum functions for the synthesis of lipid substances and for other processes of the cells promoted
by intrareticular enzymes.
Golgi Apparatus
The Golgi apparatus, shown in Figure 2-5, is closely
related to the endoplasmic reticulum. It has membranes similar to those of the agranular endoplasmic
reticulum. It is usually composed of four or more stacked layers of thin,
flat, enclosed vesicles lying near one side of the nucleus. This apparatus is prominent in secretory
cells, where it is located on the side of the cell from which the secretory substances are extruded. The
Golgi apparatus functions in association with the endoplasmic reticulum. As shown in Figure 2-5,
small ―transport vesicles‖ (also called endoplasmic reticulum vesicles, or ER vesicles) continually
pinch off from the endoplasmic reticulum and shortly thereafter fuse with the Golgi apparatus. In this
way, substances entrapped in the ER vesicles are transported from the endoplasmicreticulum to the
Golgi apparatus.
