Question

The iron-free compound of haemoglobin is
A. Globin
B. Haematin
C. Bilirubin
D. Haemotoxic

Answer 1

Hint: In vertebrates, the haemoglobin molecules are formed from the four subunits of globin protein. These subunits are composed of the protein chain that is tightly associated with a non-protein prosthetic heme group.

Complete answer:
Haemoglobin is a quaternary structure that has a characteristic of many multi-subunit of a globular protein. The amino acids in the haemoglobin mostly form alpha helices and these are connected by the non-helical segments. Inside the protein, these helical sections are stabilized by hydrogen bonds which cause the attraction within the molecules due to this, each polypeptide chain folded into a specific shape. The haemoglobin molecule is made of the four subunits of globin protein. These subunits have a protein chain which is associated with a non-protein prosthetic heme group. These protein chains are arranged in a set of alpha-helical structure segments and these are connected in a globin arrangement. The heme group contains an iron ion held in a heterocyclic ring. This is known as porphyrin. The porphyrin ring has four molecules of pyrrole which are connected by the methane bridges cyclically with the iron ion bound in the centre.
The heme is an iron-containing group and globin is an iron-free part in the haemoglobin molecule.
Hence, the correct answer is option (A).

Note: The haemoglobin is abbreviated as Hb or Hgb. It is iron-containing oxygen-transport metalloprotein in the erythrocytes.
-These are developed in the bone marrow’s cells that become RBC.
-In an adult human being, the most common type is haemoglobin A which consists of four subunits of protein that is a tetramer (two subunits of alpha and two subunits of beta).
-In the human infant, haemoglobin is made up of the two alpha chains and two gamma chains. As the infant grows, the gamma chains are gradually replaced by the beta chain.