Question

Normal adult hemoglobin (HbA) consists of-

• A. Two alpha (\(\alpha\)) and two beta (\(\beta\)) chains
• B. Two alpha (\(\alpha\)) and two gamma (\(\gamma\)) chains
• C. Two alpha (\(\alpha\)) and two delta (\(\delta\)) chains
• D. Four gamma (\(\gamma\)) chains

Hint:

Remember the major globin formulas:
- \(\text{HbA (Adult)} = \alpha_2\beta_2\)
- \(\text{HbF (Fetal)} = \alpha_2\gamma_2\)
- \(\text{HbA2 (Minor)} = \alpha_2\delta_2\)

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Hemoglobin is the iron-containing oxygen-transport metalloprotein found in the red blood cells of vertebrates.
Adult human hemoglobin is a multi-subunit protein complex composed of four polypeptide globin chains, with each subunit bound to a heme group.

Step 2: Detailed Explanation:
The specific subunit composition of human hemoglobin changes during development:
1. Normal adult hemoglobin (HbA) is the most common form of hemoglobin in adult humans, accounting for about 95% to 98% of total hemoglobin.
It is a tetramer composed of two alpha (\(\alpha\)) globin chains and two beta (\(\beta\)) globin chains, represented as \(\alpha_2\beta_2\).
2. Fetal hemoglobin (HbF) consists of two alpha (\(\alpha\)) and two gamma (\(\gamma\)) chains (\(\alpha_2\gamma_2\)), which are replaced by beta chains shortly after birth.
3. Hemoglobin A2 (HbA2) is a minor adult hemoglobin variant consisting of two alpha (\(\alpha\)) and two delta (\(\delta\)) chains (\(\alpha_2\delta_2\)).
Therefore, normal adult hemoglobin (HbA) consists specifically of two alpha and two beta chains.

Step 3: Final Answer:
The correct subunit composition corresponds to option (A).