In the quaternary structure of hemoglobin, globin chains associate into what?

In the quaternary structure of hemoglobin, globin chains associate into a specific arrangement that consists of two alpha and two beta chains, forming a tetramer. This tetrameric structure is crucial for hemoglobin's ability to transport oxygen effectively.

Individual globin chains first associate to form dimers: an alpha chain pairs with a beta chain, creating an alpha-beta dimer. These dimers then combine to form the complete tetramer. Each of the dimers contributes partners to stabilize the overall structure, which allows for the cooperative binding of oxygen. The cooperative nature of oxygen binding is fundamental for hemoglobin's role in oxygen transport.

Therefore, the correct understanding of hemoglobin's structure involves recognizing that it is organized into a tetramer that consists of two alpha chains and two beta chains, rather than only considering the dimers.