Introduction - This script shows the structure of hemoglobin. Scroll down until the text corresponding to the view is visible. (Based on 4hhb.pdb, G. Fermi et al., J. Mol. Biol. 175 159 (1984)).

Hemoglobin is a tetramer and each subunit has a bound HEME.

There are two ALPHA subunits.

and two BETA subunits.

Notice how tightly the four subunits interact with each other.