text: The lumen of this structure contains BiP, or binding immunoglobulin protein.
full_question: The lumen of this structure contains BiP, or binding immunoglobulin protein. The desmotubulepasses through the plasmodesmata and links two of these organelles in adjacent cells. In eukaryotes,signal recognition particle targets proteins and sends them to the translocons on this organelle'smembrane. In excitation-contraction coupling, large stores of (*) calcium are released from a specialized formof this organelle in myocytes. One form of this organelle metabolizes lipids and detoxifies drugs, whereas anothertype is covered with ribosomes. Membrane-bound vesicles shuttle between the Golgi apparatus and this organelle.For 10 points, name this organelle, a network of flattened sacs that comes in "smooth" and "rough" forms
first_sentence: The lumen of this structure contains BiP, or binding immunoglobulin protein.
raw_answer:  endoplasmic reticulum [or sarcoplasmic reticulum; or ER; or SR; or smooth endoplasmic reticulum; or smooth ER; or SER; or rough endoplasmic reticulum; or rough ER; or RER]