ENDOPLASMIC RETICULUM This is a membranous structure that consists of multiple stacks of membranes, usually near the nucleus. There are two types of endoplasmic reticulum or ER. There is rough endoplasmic reticulum or RER, which is studded with ribosomes. The ribosomes on RER are globular structures that are the main place that proteins get manufactured. The smooth endoplasmic reticulum or SER has no ribosomes on them. This SER is responsible for making cellular products like hormones and lipids, as well as the transport of messenger RNA from the nucleus to the protein-making part of the ER. Figure 16 illustrates the rough and smooth endoplasmic reticulum near a nucleus.
69
