Heme is the component of hemoglobin which is responsible for carrying oxygen to our cells and exchanging it for carbon dioxide. Heme contains an iron atom which changes geometry depending on whether it is attached only to heme, or to heme and oxygen. An in-depth knowledge of structure and bonding will help to explain these types of structural changes.

Heme without Oxygen Bound (333K)

Heme with Oxygen Bound (333K)