Definition and Types of Hemoglobin (Hb).pptx

Hemoglobin

1. Definition and Types of Hemoglobin (Hb) Dr. Jagroop Singh Sidhu ( Ph.D Biochemistry) Government Medical College Amritsar

2. Hemoglobin (Hb) is a complex protein found in red blood cells that is responsible for carrying oxygen from the lungs to the tissues and organs of the body, and transporting carbon dioxide back to the lungs to be exhaled. Hemoglobin is composed of four protein subunits, each containing a heme group that can bind to one molecule of oxygen.

3. Types of Hemoglobin There are several different types of hemoglobin, which vary in their composition and function. The main types include: Hemoglobin A ( HbA ) : The most common type of hemoglobin in adults, comprising about 95-98% of total hemoglobin. Consists of two alpha (α) and two beta (β) chains. Hemoglobin A2 (HbA2) : Makes up about 2-3% of adult hemoglobin. Composed of two alpha (α) and two delta (δ) chains.

4. Hemoglobin F ( HbF ) : Also known as fetal hemoglobin. Predominant in the fetus and newborn, usually replaced by HbA after birth. Consists of two alpha (α) and two gamma (γ) chains. Has a higher affinity for oxygen than HbA , facilitating the transfer of oxygen from the mother to the fetus. Hemoglobin S ( HbS ) : An abnormal variant associated with sickle cell disease. Results from a mutation in the beta (β) chain. Causes red blood cells to become rigid and sickle-shaped, leading to various complications such as pain, anemia, and organ damage.

5. Hemoglobin C ( HbC ) : Another abnormal variant resulting from a mutation in the beta (β) chain. Can cause mild hemolytic anemia and splenomegaly. Hemoglobin SC disease occurs when a person inherits both HbS and HbC genes, leading to symptoms similar to sickle cell disease but generally milder. Hemoglobin E ( HbE ) : Common in Southeast Asia. Results from a mutation in the beta (β) chain. Can cause mild hemolytic anemia and, when combined with HbS , results in hemoglobin SE disease with symptoms similar to sickle cell disease. Hemoglobin H ( HbH ) : Seen in some forms of alpha-thalassemia. Composed of four beta (β) chains. Has a high affinity for oxygen but less efficient in releasing it to tissues.

6. Hemoglobin Bart's (Hb Bart's) : Composed of four gamma (γ) chains. Seen in severe forms of alpha-thalassemia, particularly in newborns. Inefficient at releasing oxygen to tissues, leading to hydrops fetalis and often resulting in fetal death.

7. Structure of a Hemoglobin Molecule A typical hemoglobin molecule consists of: Four globin chains : Two alpha (α) chains and two beta (β) chains (in HbA ). Four heme groups : Each heme group contains one iron ion (Fe2+) that can bind to one molecule of oxygen (O2).

8. Functions of Hemoglobin Oxygen Transport : Hemoglobin binds oxygen in the lungs and releases it in the tissues. Carbon Dioxide Transport : Hemoglobin helps transport carbon dioxide from the tissues back to the lungs for exhalation. Buffering : Hemoglobin acts as a buffer to help maintain the acid-base balance in the blood.

9. Summary Hemoglobin is a vital protein in red blood cells, with various types adapted for different functions and life stages. Understanding its structure and function is essential in diagnosing and treating disorders related to abnormal hemoglobin variants.

10. Detailed Mechanism of Oxygen Binding and Release Oxygen Binding (in the Lungs) : In the lungs, the partial pressure of oxygen (pO2) is high. Oxygen molecules diffuse from the alveoli into the blood and bind to the iron atoms in the heme groups of hemoglobin. The binding of one oxygen molecule increases the affinity of hemoglobin for oxygen (cooperative binding), making it easier for additional oxygen molecules to bind. Oxygen Release (in the Tissues) : In tissues, the partial pressure of oxygen (pO2) is low due to cellular respiration. Hemoglobin releases its bound oxygen, which diffuses into the cells where it is used for metabolic processes. The release of one oxygen molecule decreases the affinity of hemoglobin for oxygen, facilitating the release of more oxygen molecules.

11. Bohr Effect The Bohr effect describes how changes in carbon dioxide concentration and pH can influence hemoglobin's oxygen-binding affinity: High CO2/Low pH : In actively metabolizing tissues, increased CO2 production and a lower pH (more acidic) reduce hemoglobin's affinity for oxygen, promoting oxygen release. Low CO2/High pH : In the lungs, where CO2 is exhaled and the pH is higher (less acidic), hemoglobin's affinity for oxygen increases, promoting oxygen binding.

12. Thank YOU