Question

Defferentiate between myoglobin and haemoglobin

Answer 1

Myoglobin

Myoglobin occurs as a monomeric protein in which the globin surrounding a heme. It acts as a secondary carrier of oxygen in the muscle tissue. When the muscle cells are in action, they need a large amount of oxygen. Muscle cells use these proteins to accelerate oxygen diffusion and take oxygen for times of intense respiration. The tertiary structure of myoglobin is similar to a typical water soluble globule protein structure.

Polypeptide chain of myoglobin has 8 separate right handed α-helices. Each protein molecule contains one heme prothetic group and each heme residue contains one central coordinately bound iron atom. Oxygen is bound directly to the iron atom of the heme prosthetic group.

Hemoglobin

Hemoglobin occurs as a tetrameric protein in which each subunit consists of a globin surrounding a heme. It is the system-wide carrier of oxygen. It binds oxygen molecules and then it is transported through the blood by red blood cells.

In vertebrates, oxygen is diffused through the lung tissue into the red blood cells. Since hemoglobin is a tetramer, it can bind four oxygen molecules at once. Bound oxygen is then distributed through the entire body and offloaded from red blood cells to respiring cells. Hemoglobin then takes the carbon dioxide and return them back to the lungs. Therefore, hemoglobin serves to deliver oxygen needed for cellular metabolism and removes the resulting waste product, carbon dioxide.

Hemoglobin consists of several polypeptide chains. Human hemoglobin is composed of two α (alpha) and two β (beta) subunits. Each α-subunit has 144 residues, and each β-subunit has 146 residues. Structural characteristics of both α (alpha) and β (beta) subunits are similar to myoglobin.