Imagine a transmembrane molecule that lies in the plasma membrane and acts as a receptor for an extracellular signaling molecule. When the ligand-binding domain is inserted into the er during synthesis of this transmembrane molecule, will it lie on the lumen side of the er or the cytoplasm side?.

Answer

lumen side of the ER membrane

Q: What is a transmembrane molecule? A: A transmembrane molecule is a type of protein that spans the entire cell membrane.
Q: What is the plasma membrane? A: The plasma membrane is the outermost boundary of a cell that separates the cytoplasm from the extracellular environment.
Q: What happens when a ligand-binding domain is inserted into the ER during synthesis of a transmembrane protein? A: The ER is the site of protein synthesis, folding and modification in eukaryotic cells. When the ligand-binding domain of a transmembrane protein is inserted into the ER during its synthesis, it will be inserted into the membrane of the ER.
Q: Will the ligand-binding domain lie on the lumen or cytoplasm side of the ER membrane? A: The lumen side of the ER is the side of the membrane that faces the interior of the ER. Therefore, if the ligand-binding domain is inserted into the membrane of the ER during synthesis of the transmembrane protein, it will lie on the lumen side of the ER membrane.