Endoplasmic Reticulum
It's a network of membrane tubules within the cytoplasm of a eukaryotic cell, that is continuous with the nuclear membrane. It usually has ribosomes attached and is involved in the protein and lipid synthesis. Transportation is not the only job that ER does. They manufacture all of the proteins because that is the ER's function because of the ribosomes on RER. The ER is very important. The ER is the one that transports all of the proteins that are produced from here to there and also the golgi apparatus. Even though ribosomes are the ones that produce proteins, without the ER they will not be able to provide the proteins that they produce to others.