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
Which is an allosteric protein -a) Transferrinb) Ceruloplasminc) Phosphofructokinase d) Haemoglobin 
Select and explain. 
A. ac, B. b, C. cd, D. d
C: cd
Answer: C: cd 
Explanation: Hemoglobin is an allosteric protein, i.e. binding of an allosteric modulator to hemoglobin alter binding of other substrate or molecule (i.e. O2).
Phosphofructokinase I is an allosteric enzyme and is regulated allosterically in glycolysis. All enzymes (except for ribozymes) are proteins. So PFK-I is an allosteric protein.