<prompt> Proteins targeted for destruction in eukaryotes are covalently linked toClathrinPepsinLamininUbiquitin  <response>: D Ubiquitin UBIQUITIN is a small protein present in eukaryotic cells, that targets many intracellular proteins for degradation, mainly Abnormal newly produced proteins Aged normal proteins The C terminal residue of ubiquitin becomes covalently attached to lysine residues of proteins that are then degraded via an adenosine triphosphate dependent process. Other options: Clathrin: Clathrin is a peripheral membrane protein that helps in endocytosis. The vesicles formed during absorptive pinocytosis are derived from invaginations pits that are coated on the cytoplasmic site with a filamentous material known as clathrin. Pepsin: Is a proteolytic enzyme secreted by chief cells of stomach It is used for digestion Laminin: Is found in extracellular matrix It is the most abundant glycoprotein present in basement membrane 