What polypeptide chains are found in normal adult hemoglobin A?

Normal adult hemoglobin A (HbA) is composed of two alpha (α) and two beta (β) polypeptide chains, which are essential for its function in oxygen transport. The structure of HbA allows it to efficiently bind oxygen in the lungs and release it in the tissues.

The alpha chains are produced by genes located on chromosome 16, while the beta chains are produced by genes on chromosome 11. This specific combination, with two of each chain type, is critical as it is the standard configuration for adult hemoglobin, providing the required stability and functionality. The presence of both alpha and beta chains enables hemoglobin A to maintain its quaternary structure necessary for proper oxygenation and release during the circulatory process.

Other combinations that involve different chain types, such as gamma (g) or delta (d), are typically found in fetal hemoglobin (HbF) or in certain forms of abnormal hemoglobin rather than in normal adult hemoglobin. Therefore, the identification of appropriately composed poly peptide chains is crucial for defining the characteristics of hemoglobin in adults.