What is endoplasmic recticulum in an animal cell?

Question

in the cell diagram, they have something pointing to the endoplasmic recticulum, but they never really said what the endoplasmic recticulum does.

So what does it do, what is its purpose of being in the cell

Answer 1

The endoplasmic reticulum is responsible for several specialized functions: protein translation, folding and transport of proteins to be used in the cell membrane (e.g. transmembrane receptors and other integral membrane proteins), or to be secreted (exocytosed) from the cell (e.g. digestive enzymes); sequestration of calcium; and production and storage of glycogen, steroids, and other macromolecules. The endoplasmic reticulum is part of the endomembrane system. The basic structure and composition of the ER membrane is similar to the plasma membrane.