Обозначен для указания различных типов белковых цепей, с. Diagram of a hemoglobin molecule structure, illustrating the arrangement of alpha (? ) and beta (? ) subunits. Four subunits are depicted as stylized blue and cyan arrows encircling red circles labeled "H," representing iron ions within heme groups. The structure is labeled "? " and "? " to denote the different types of protein chains, with an 'Ire' label centrally. The design demonstrates the quaternary structure of hemoglobin, essential for oxygen transport in blood.