Final answer:
The endoplasmic reticulum (ER) is a series of interconnected membranous sacs and tubules that collectively modifies proteins and synthesizes lipids. These two functions are performed in separate areas of the ER: the rough ER and the smooth ER, respectively.
Step-by-step explanation:
The endoplasmic reticulum (ER) is a series of interconnected membranous sacs and tubules that collectively modifies proteins and synthesizes lipids. These two functions are performed in separate areas of the ER: the rough ER and the smooth ER, respectively.