This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Functions of apoproteins are/is 
Select and explain. 
A. Structural component of lipoprotein, B. Enzyme cofactors, C. Enzyme inhibitors, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Apolipoproteins carry out several roles:
(1) they can form part of the structure of the lipoprotein, for example, apo B;

(2) they are enzyme cofactors, for example, C-II for lipoprotein lipase,  A-I  for  lecithin:cholesterol  acyltransferase,  or  enzyme inhibitors, for example, apo A-II and apo C-III for lipoprotein lipase, apo C-I for cholesteryl ester transfer protein; and 
(3) they Apolipoproteins carry out several roles:
(1) they can form part of the structure of the lipoprotein, for example, apo B;
(2) they are enzyme cofactors, for example, C-II for lipoprotein lipase,  A-I  for  lecithin:cholesterol