Answer:
Endoplasmic reticulum.
Explanation:
Endoplamsmic reticulum may be defined as one of the membrane bound cell organelle and continuous with the nuclear envelope. Two different types of endoplasmic reticulum are rough endoplasmic reticulum and smooth endoplasmic reticulum.
Endoplasmic reticulum contains an extensive network of the tubes sacs and vesicles. These structure helps in the transportation of proteins and also helps in the protein processing.
Thus, the answer is endoplasmic reticulum.
