Question

Haemoglobin is
(a)Monomeric protein
(b)Oligomeric protein
(c)Chromoprotein
(d)Both b and c

Answer 1

Hint: Haemoglobin is a protein found in the erythrocytes (red blood cells). It imparts red color to the cells and functions to carry oxygen to all the parts of the body and consists of iron.

Complete answer:

Chemically, it is a conjugated protein. It consists of two parts- haem is the prosthetic part and globin is the protein part. It is a tetramer protein. In other words, it has 4 polypeptide subunits (globin subunits), having 2 α and 2 β globin chains. These two dimmers are interlinked. Thus, haemoglobin has an oligomeric structure. Also, the heme part gives a red color. So it is also a chromoprotein.

Additional Information: Haemoglobin is a major hemoprotein of our body. The heme part has iron and 4 pyrrole rings, so also termed as Ferroprotoporphyrin IX. The iron of heme is hexavalent and forms six-coordinate bonds. Four bonds with the nitrogen of pyrrole rings, 5th bond with globin chain, and 6th with oxygen. Iron helps in binding oxygen with Hb. Since Hb serves in the transport and exchange of gases between lungs and tissues, it is also termed as respiratory protein. It is present in vertebrates while also found in some invertebrates like an earthworm, Neiries.
So, the correct answer is ‘Both b and c’.

Note: -Each RBC has approx 250-350 million Hb molecules. About 97% of oxygen is transported by RBCs in our blood.
-Each globin chain folds to form 3 dimensional tertiary structure subunit. In native conformation, Hb has a quaternary structure.
-Carbon dioxide does not bind with Hb and is transported by the globin chain.