Final answer:
The composition of HbA is α2β2, which refers to two alpha (α) and two beta (β) chains. HbA is the regular hemoglobin found in adults, distinct from HbA2 and HbF, which have different compositions.
Step-by-step explanation:
The composition of HbA, which is found in normal adult human beings, is α2β2. This means that HbA consists of two alpha (α) chains and two beta (β) chains, each combining to form the complete hemoglobin molecule that carries oxygen in the blood.
The adult version of hemoglobin, HbA, should not be mistaken for HbA2 or foetal hemoglobin (HbF), which have different compositions. HbA2 consists of α2β2 chains and is present in some normal human adults, whereas HbF is found in the growing fetus and consists of α2γ2 chains.
Hemoglobin is a large molecule with a molecular weight of 65,000, made up of proteins and iron, with its structure comprising globin chains that hold heme groups containing iron ions vital for oxygen transport. Abnormal hemoglobins, such as HbS, arise from mutations in the genes coding for the alpha or beta chains and can lead to conditions like sickle cell disease.