What are the key functions of the endoplasmic reticulum?

The key functions of the endoplasmic reticulum (ER) are accurately captured in the choice that highlights protein and lipid synthesis, along with material transport. The endoplasmic reticulum consists of two distinct types: rough ER, which is studded with ribosomes, plays a crucial role in the synthesis of proteins that are either secreted from the cell, incorporated into the cell’s plasma membrane, or sent to an organelle. The smooth ER, lacking ribosomes, is involved in the synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions.

In addition to synthesis, the ER serves as a transport network, facilitating the movement of proteins and lipids to various locations within the cell, particularly to the Golgi apparatus for further processing and distribution. This multifaceted role makes it a central player in maintaining the cell's structural and functional integrity.