Hemoglobin
Medical Author: Siamak Nabili, MD, MPH
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
What is hemoglobin?
Hemoglobin is the protein molecule in red blood cells that carries oxygen from the lungs
to the body's tissues and returns carbon dioxide from the tissues to the lungs.
Hemoglobin is made up of four protein molecules (globulin
chains) that are connected together. The normal adult hemoglobin (Hbg) molecule
contains 2 alpha-globulin chains and 2 beta-globulin chains. In fetuses and
infants, there are only a few beta chains and the hemoglobin molecule is made up
of 2 alpha chains and 2 gamma chains. As the infant grows, the gamma chains are gradually replaced by beta chains.
Each globulin chain contains an important central
structure called the heme molecule. Embedded within the heme molecule is iron
that transports the oxygen and carbon dioxide in our blood. The iron contained in hemoglobin is also responsible for the red color of blood.
Hemoglobin also plays an important role in maintaining
the shape of the red blood cells. Abnormal hemoglobin structure can, therefore, disrupt the shape of red blood cells and impede its function and its flow through blood vessels.
Next: How is hemoglobin measured? »
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