This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biological Function of Proteins, Subject name: Biochemistry
[{'content': 'Defective proteins are degraded after attaching covalently to - \nSelect and explain. \nA. Clathrin, B. Pepsin, C. Laminin, D. Ubiquitin', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Ubiquitin o Defective proteins are often marked for destruction by ubiquitination (attachment of small, highly conserved protein called ubiquitin). Such proteins are rapidly degraded by proteosome, which is a macromolecular, ATP dependent, proteolytic system located in the cytosol.", 'role': 'assistant'}]