Hb or Hgb refers to which protein in red blood cells?

• A. Hemoglobin
• B. Hemorrhage
• C. Exsanguination
• D. Alcohol

Answer: (A)

Hb, or Hgb, is the protein in red blood cells that carries oxygen. It binds oxygen in the lungs through iron in the heme groups and releases it to tissues throughout the body; it also helps move some carbon dioxide back to the lungs to be exhaled. In adults, it’s a four-subunit molecule (two alpha and two beta chains) that shows cooperative binding, meaning binding of oxygen at one site affects binding at the other sites, optimizing oxygen uptake and release. The other terms refer to things that aren’t the oxygen-carrying protein in red blood cells—bleeding (hemorrhage or exsanguination) or a chemical (alcohol). So Hb/Hgb is the hemoglobin protein.