• Oxygen carrying pigment of the erythrocytes; a complex protein composed of four heme groups and four globin polypeptide chains.
  CRISP Thesaurus
  National Institutes of Health, 2006
• The oxygen-carrying substance that gives red blood cells their color.
  Harvard Dictionary of Health Terms
  Harvard Medical Publishing, 2011
• The red respiratory protein of erythrocytes, consisting of approximately 3.8% heme and 96.2% globin (64.5 KD), which as oxyhemoglobin (HbO2) transports oxygen from the lungs to the tissues where the oxygen is readily released and HbO2 becomes Hb.
  NCI Thesaurus
  U.S. National Cancer Institute, 2021
• The substance inside red blood cells that binds to oxygen in the lungs and carries it to the tissues.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• The oxygen-carrying proteins of ERYTHROCYTES. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements.
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2021
• Hemoglobin, iron-containing protein in the blood of many animals--in the red blood cells (erythrocytes) of vertebrates--that transports oxygen to the tissues. Hemoglobin forms an unstable reversible bond with oxygen. In the oxygenated state, it is called oxyhemoglobin and is bright red; in the...
  Encyclopedia Britannica
  Encyclopedia Britannica, Inc., 2020