All three of the organelles are made of a series of membranes.
1. The smooth endoplasmic reticulum (SER) lies adjacent to the rough endoplasmic reticulum (RER). It looks likes a long maze of a membrane. It acts as a manufacturing and storage center of the cell. Most commonly, the SER delivers the proteins created by the ribosomes of the RER. However, what is manufactured and stored is dependent upon the type of cell. For example, the SER releases calcium ions that are needed to help the muscles contract. In a cell of the endocrine system, the SER releases steroids or hormones.
2. The Golgi apparatus looks similar to the smooth endoplasmic reticulum. It is made of a series of flat membrane sacs that are unconnected and known as cisternae. The Golgi apparatus packages, ships, and delivers proteins. As the proteins travel through the cisternae, sugars are added. It is these sugars that act as directions to determine where they should be delivered in the cell.
3. The rough endoplasmic reticulum (RER) is, again, made of a series of membranes. The attached ribosomes to its exterior make the membranes appear rough. Although found scattered throughout the cell, the majority of the RER lies directly adjacent to the nucleus. The ribosomes on the RER help make proteins, along with RNA, during protein synthesis. Therefore, the RER is associated with protein production.