Difference Between Normal Hemoglobin and Sickle Cell Hemoglobin | Normal Hemoglobin vs Sickle Cell Hemoglobin

Key Difference – Normal Hemoglobin vs Sickle Cell Hemoglobin

Hemoglobin (Hgb) is the main protein molecule which provides the typical shape of the red blood cell – round shape with a narrow center. The hemoglobin molecule is made up of four sub protein molecules in which two chains are alpha globulin chains, and the other two are beta globulin chains. Iron atoms in hemoglobin and the shape of the red blood cells are important for oxygen transportation through blood. If the shape of hemoglobin is destroyed, it fails to transport oxygen through the blood. Sickle cell hemoglobin is one type of an abnormal hemoglobin molecule which causes an anemia conditions called sickle cell anemia. The key difference between normal hemoglobin and sickle cell hemoglobin is that normal hemoglobin has glutamic acid in the 6th position of the amino acid sequence of the beta globulin chain whereas sickle cell hemoglobin has Valine in the 6th position of the beta globulin chain. Normal hemoglobin and sickle cell hemoglobin only differ by a single amino acid in beta chains.

1. Overview and Key Difference
2. What is Normal Hemoglobin
3. What is Sickle Cell Hemoglobin
4. Side by Side Comparison – Normal Hemoglobin vs Sickle Cell Hemoglobin
5. Summary

What is Normal Hemoglobin?

Hemoglobin is an iron-containing metalloprotein found in red blood cells. It is responsible for the transportation of oxygen from the lung to the body tissues and organs, and transportation of carbon dioxide from body tissues to the lung. It is also known as oxygen-carrying protein in the blood. It is a complex protein, which consists of four small protein subunits and four heme groups bearing iron atoms as shown in figure 01. Hemoglobin has a high affinity for oxygen. There are four oxygen binding sites located inside a hemoglobin molecule. Once hemoglobin saturates with oxygen, the blood becomes bright red in colour and is known as oxygenated blood. The second state of the hemoglobin, which lacks oxygen, is known as deoxyhemoglobin. In this state, blood bears the dark red colour.

Iron atoms embedded in the heme compound of hemoglobin mainly facilitates the oxygen and carbon dioxide transportation. Binding of oxygen molecules to Fe+2 ions changes the conformation of the hemoglobin molecule. The iron atoms in the hemoglobin also help to maintain the typical shape of the red blood cell. Therefore, iron is a vital element found in the red blood cells.