Final answer:
Membrane-bound enzymes that transfer sugar residues to growing carbohydrate chains on glycoproteins are called glycosyltransferases (option 2). These enzymes are essential for the biosynthesis of glycoproteins, which ultimately become part of the plasma membrane's glycocalyx.
Step-by-step explanation:
Membrane-bound enzymes that transfer sugar residues to growing carbohydrate chains on glycoproteins are called glycosyltransferases. These enzymes play a crucial role in the synthesis of glycoproteins, which occurs as proteins traverse the endomembrane system, particularly within the rough endoplasmic reticulum (RER) and the Golgi apparatus. The process involves initial glycosylation in the RER, followed by terminal glycosylation in the Golgi apparatus. Eventually, the complete glycoproteins, with their carbohydrate chains attached, are inserted into the plasma membrane, contributing to the cell's glycocalyx, which is integral for cell-cell recognition, communication, and various other functions.