There are two types of ER:
* Rough ER: Has ribosomes attached to its surface, giving it a "rough" appearance. It's involved in protein synthesis and modification.
* Smooth ER: Lacks ribosomes, giving it a "smooth" appearance. It's involved in lipid synthesis, detoxification, and calcium storage.
Both types of ER contain cisternae, which are interconnected flattened sacs that create a network for the movement of molecules within the cell.
