Oxygen itself isn't red. The red color associated with oxygen in the body comes from its interaction with hemoglobin in red blood cells. Specifically, oxygen becomes red when it binds to the heme group within hemoglobin.
The Role of Hemoglobin
Hemoglobin is a protein found in red blood cells that's responsible for carrying oxygen throughout the body. It consists of four subunits, each containing a heme group.
What is Heme?
The heme group is a porphyrin ring complex with an iron atom at its center. This iron atom is crucial for oxygen binding.
How Oxygen Binds to Hemoglobin and Turns Red
- Deoxyhemoglobin: When hemoglobin is not bound to oxygen (deoxyhemoglobin), it has a bluish-purple hue.
- Oxygen Binding: When oxygen binds to the iron atom in the heme group, it causes a conformational change in the hemoglobin molecule.
- Coordination Complex: The binding of oxygen to iron creates a coordination complex. This complex significantly alters the way the molecule absorbs and reflects light.
- Color Change: This change in light absorption results in the characteristic bright red color of oxyhemoglobin (hemoglobin bound to oxygen). The blood in your arteries, which is rich in oxygen, appears bright red for this reason.
In summary, the interaction between oxygen and the iron atom within the heme group of hemoglobin is what gives oxygenated blood its red color. Free oxygen, in its gaseous form, is colorless.
