HbA (Hemoglobin A) is the most common type of hemoglobin found in adult humans. It constitutes about 95-98% of the total hemoglobin in adults.
Here's a more detailed breakdown:
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Composition: HbA is a tetramer, meaning it's made up of four subunits. Specifically, it consists of two alpha (α) globin subunits and two beta (β) globin subunits. This is represented as α₂β₂.
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Function: Hemoglobin's primary function is to transport oxygen from the lungs to the tissues throughout the body. HbA accomplishes this by binding oxygen molecules to the iron atoms within the heme groups of each globin subunit.
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Developmental Changes: While HbA is dominant in adults, its production increases dramatically after birth. Before birth, fetal hemoglobin (HbF) is the primary type.
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Other Hemoglobin Types: It's important to distinguish HbA from other types like:
- HbA₂: Another adult hemoglobin type, but it's less common, making up only about 2-3% of total adult hemoglobin. It consists of two alpha and two delta (δ) globin subunits (α₂δ₂).
- HbF (Fetal Hemoglobin): Predominant in fetuses and newborns. It has two alpha and two gamma (γ) globin subunits (α₂γ₂).
In summary, HbA is the major adult form of hemoglobin composed of two alpha and two beta globin chains, crucial for oxygen transport.
