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
Heme in hemoglobin is in the 
Select and explain. 
A. Hydrophobic pocket, B. Positive region, C. Negative region, D. Polar region
A: Hydrophobic pocket
Answer: A: Hydrophobic pocket 
Explanation: Hemoglobin is found exclusively in red blood cells (RBC), where its main function is to transpo oxygen (O2) from the lungs to the capillaries of the tissues. Hemoglobin A, the major hemoglobin in adults, is composed of four polypeptide chains (two a chains and two b chains) held together by noncovalent interactions. Each chain (subunit) has stretches of a-helical structure and a hydrophobic heme-binding pocket similar to that described for myoglobin. Ref: LIPPINCOTT's Biochemistry 6th Edition page no. 27