What is deoxyhemoglobin?

• A. A hemoglobin molecule whose iron is bound to oxygen
• B. Hemoglobin bound to carbon dioxide
• C. Hemoglobin bound to oxygen
• D. A hemoglobin molecule whose iron is not bound to oxygen

Answer: (D)

Deoxyhemoglobin is the form of hemoglobin in which the iron of the heme is not bound to oxygen. This state occurs after hemoglobin has released O2 to tissues and is returning to the lungs to pick up more oxygen. It’s different from oxyhemoglobin (where iron is bound to O2) and from carbaminohemoglobin (hemoglobin bound to CO2 at sites on the globin, not at the iron).