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
Blood group antigens belong to the class 
Select and explain. 
A. Conjugated proteins, B. Unconjugated protein, C. Simple protein, D. Hemoglobin binding protein
A: Conjugated proteins
Answer: A: Conjugated proteins 
Explanation: For red blood cells, the membrane oligosaccharides that determine the antigenic natures of the ABO substances appear to be mostly present in glycosphingolipids, whereas in secretions the same oligosaccharides are present in glycoproteins. Some examples of conjugated proteins are lipoproteins, glycoproteins, phosphoproteins, hemoproteins, flavoproteins, metalloproteins, phytochromes, cytochromes, opsins and chromoproteins. so the ABO substances can be chosen as Conjugated proteins from the given options Ref: Harper's Illustrated Biochemistry, 30E (2015) Pg No. 697 chapter 53.