Which organelle conveys or transports materials throughout the cell?

The endoplasmic reticulum.

Both the smooth and the roughendoplasmic reticulum consist of membranous channels that all connect with one another and with the nuclear membrane. They are both involved in the transport of materials from one part of the cell to another.

The smooth endoplasmic reticulum is also involved in the synthesis of lipids, and the rough endoplasmic reticulum, which has ribosomes embedded in its membrane, is the site of much of the cell's protein synthesis.