Endoplasmic Reticulum
Endoplasmic Reticulum - Wrapping it Up

Another organelle in the cell is the endoplasmic reticulum (ER). While the function of the nucleus is to act as the cell brain, the ER functions as a packaging system. It does not work alone. The ER works closely with the Golgi apparatus, ribososmes, RNA, mRNA, and tRNA. It creates a network of membranes found through the whole cell. The ER may also look different from cell to cell, depending on the cell's function.

Rough and Smooth

As you learn more about cells you will discover two types of ER. There are rough ER and smooth ER. They both have the same types of membranes but they have different shapes and rough ER has ribosomes attached. Rough ER looks like sheets of bumpy membranes while smooth ER looks more like tubes. Sometimes the ER looks like a flat balloon. Sacs of the ER called cisternae store the complex molecules.

Smooth ER has its purpose in the cell. It acts as a storage organelle. It is important in the creation and storage of steroids. It also stores ions in solution that the cell may need at a later time. Steroids are a type of ringed organic molecule used for many purposes in an organism. They are not always about building muscle mass like a weight lifter. The ion storage is important because sometimes a cell needs ions fast. It might not want to search the environment for ions, so it is easier to have them stored in a pack for easy use.

Rough ER was mentioned in the section on ribosomes. They are very important in the synthesis and packaging of proteins. Some of those proteins might be used in the cell and some are sent out. The ribosomes are attached to the membrane of the ER. As the ribosome builds the amino acid chain, the chain is pushed into the ER. When the protein is complete, the rough ER pinches off a vesicle. That vesicle, a small membrane bubble, can move to the
cell membrane or the Golgi apparatus.