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
Number of prosthetic groups in a hemoglobin molecule ? 
Select and explain. 
A. 1, B. 2, C. 3, D. 4
D: 4
Answer: D: 4 
Explanation: Ans. is 'd' i.e., 4 Hemoglobin is a conjugated protein which has a tetrameric structure. It is an assembly of four globular proteins. Each subunit is composed of a protein pa, i.e. globin and a nonprotein prosthetic group, i.e. heme. Each hemoglobin molecule is made up of 4 heme molecules and 4 polypeptide chains (2 pairs of similar polypeptide chains). Hemoglobin=Globin (containing 4 polypeptide chains)+ 4 heme molecules