1. By itself, heme is not a good oxygen carrier. It must be part of a larger protein to prevent oxidation of the iron.

2. The iron atom of the heme group is almost entirely enclosed within the protein.

3. Each iron atom can form six coordination bonds: One of these bonds is formed between iron and oxygen.

4. Each hemoglobin or myoglobin molecule can bind four oxygen molecules.

5. Hemoglobin is a heterotetramer, whereas myoglobin is a monomer.

6. Both hemoglobin and myoglobin contain a prosthetic group called heme, which contains a central iron atom.

7. Molecular oxygen binds irreversibly to the Fe(II) atom in heme.