Answer:
Endoplasmic Reticulum
The endoplasmic reticulum (ER) (plural, reticuli) is a network of phospholipid ramembnes that form hollow tubes, flattened sheets, and round sacs. These flattened, hollow folds and sacs are called cisternae. The ER has two major functions:
Transport: Molecules, such as proteins, can move from place to place inside the ER, much like on an intracellular highway.
Synthesis: Ribosomes that are attached to ER, similar to unattached ribosomes, make proteins. Lipids are also produced in the ER.
