Final answer:
Hemoglobin and hemocyanin are metalloproteins that reversibly bind oxygen. Hemoglobin contains an iron-based heme group and is a tetramer, while hemocyanin contains copper and can form larger complexes, with oxygen binding reversibly in both cases.
Step-by-step explanation:
Both hemoglobin and hemocyanin are metalloproteins, meaning they are proteins that contain a metal ion as part of their structure. Hemoglobin, found in red blood cells, is comprised of four subunits, specifically two alpha and two beta polypeptide chains, each of which surrounds an iron-containing heme group.
This heme group is crucial for the protein's ability to bind oxygen reversibly. Unlike hemoglobin, hemocyanin, which is found in some invertebrates, uses copper instead of iron for oxygen binding. Hemoglobin and hemocyanin do not always form tetramers; hemocyanin, for instance, can form larger complexes.
And contrary to irreversible binding, the oxygen binding to these metalloproteins is reversible, which is essential for the transport and release of oxygen as needed by the body.