Final answer:
Chaperone proteins are responsible for binding to improperly folded or improperly assembled proteins in the ER until proper folding occurs.
Step-by-step explanation:
Chaperone proteins are the type of proteins that bind to improperly folded or improperly assembled proteins in the endoplasmic reticulum (ER), holding them there until proper folding occurs. Chaperones assist proteins in folding, preventing aggregation and helping them adopt their correct shape. They act as molecular chaperones to ensure that proteins fold correctly and function properly.