This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
[{'content': 'One of the following is an example of phosphoprotein \nSelect and explain. \nA. Histone, B. Casein, C. Ceruloplasmin, D. Albumin', 'role': 'user'}, {'content': "Answer: B \nExplanation: The phosphate groups add negative charges to the polypeptides. The functional significance of this modification varies from one protein to the next. For example, the milk protein casein has many phosphoserine groups that bind Ca2+. Calcium, phosphate, and amino acids are all valuable to suckling young, so casein efficiently provides three essential nutrients. And as we have seen in numerous instances, phosphorylation dephosphorylation cycles regulate the activity of many enzymes and regulatory proteins. Ref: Lehninger's Principles of Biochemistry 7th Editoin - D L Nelson, Cox Lehninger - W H Freeman Pg no 2901 Ref: Lehninger's Principles of Biochemistry 4th Editoin - D L Nelson, Cox Lehninger - W H Freeman Pg no 1063.", 'role': 'assistant'}]