What is the function of the endoplasmic reticulum in a cell?

The endoplasmic reticulum (ER) is an important cell organelle present in both plant and animal cells. It forms a network of membranes connected to the nuclear envelope and plays a major role in protein and lipid synthesis, transport, and detoxification.

There are two types of ER:

• Rough Endoplasmic Reticulum (RER): Has ribosomes attached to its surface and is involved in the synthesis of proteins that are secreted from the cell or sent to the cell membrane.
• Smooth Endoplasmic Reticulum (SER): Lacks ribosomes and helps in lipid synthesis, carbohydrate metabolism, and detoxification of harmful substances.

The ER also acts as a transport system, moving materials between the nucleus, cytoplasm, and Golgi apparatus. In muscle cells, a specialized form called the sarcoplasmic reticulum stores and releases calcium ions, aiding muscle contraction. Overall, the endoplasmic reticulum is essential for maintaining cell organization and metabolic efficiency.