Final answer:
Hemoglobin consists of two alpha and two beta polypeptide chains which together demonstrate quaternary structure, integral for its function in oxygen transport.
Step-by-step explanation:
The oxygen-carrying molecule hemoglobin is composed of four polypeptide chains, two of which are called alpha-hemoglobin and the other two called beta-hemoglobin. 'The level of protein structure demonstrated by hemoglobin is quaternary structure.' This refers to the way these polypeptide chains interact and assemble into a complex.
Hemoglobin, found in red blood cells, has a crucial role in transporting oxygen throughout the body. The quaternary structure is the association of four subunits, each containing an iron atom within a heme group, which is necessary for oxygen binding.
The functionality of hemoglobin, such as oxygen binding and release, is heavily dependent on its quaternary structure. The intricate arrangement of the alpha and beta subunits allows hemoglobin to undergo slight structural changes when binding to or releasing oxygen, critical for its role in the circulatory system.