This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
[{'content': 'Which amino acid in a protein acts as a potential O-glycosylation site for attachment of an oligosaccharide unit? \nSelect and explain. \nA. Glutamine, B. Cysteine, C. Serine, D. Aspargine', 'role': 'user'}, {'content': "Answer: C \nExplanation: O Glycosylation occurs between OH group of the amino acid and oligosaccharide, while N glycosylation occurs between the amino group of the amino acid and an oligosaccharide chain.Tyrosine, serine, and threonine are OH group-containing amino acid which gets attached with the oligosaccharide chain with the help of O glycosidic linkage. Glutamine, aspargine are amide group-containing amino acid which gets attached with the oligosaccharide chain with the help of N-glycosidic linkage.(Ref: Harper's, 25/e, pg 682)", 'role': 'assistant'}]