Hemoglobin by molecules such as carbon monoxide (for example, from tobacco smoking, exhaust gas, and incomplete combustion in furnaces). CO competes with oxygen at the heme binding site. Hemoglobin's binding affinity for CO is 250 times greater than its affinity for oxygen, meaning that small amounts of CO dramatically reduce hemoglobin's ability to transport oxygen. Since carbon monoxide is a colorless, odorless and tasteless gas, and poses a potentially fatal threat, carbon monoxide detectors have become commercially available to warn of dangerous levels in residences. When hemoglobin combines with CO, it forms a very bright red compound called carboxyhemoglobin, which may
Embryonic hemoglobin Embryonic hemoglobin The human embryonic haemoglobins were discovered in 1961. These were Hb-Gower 1, consisting of 2 zeta chains and 2 epsilon chains, and Hb-Gower 2, which consists of 2 αlpha-chains and 2 epsilon-chains, the zeta and epsilon chains being the embryonic haemoglobin chains. Embryonic hemoglobin is a tetramer produced in the blood islands in the embryonic yolk sac during the mesoblastic stage (first week of pregnancy until the end of the pregnancy). The protein is commonly referred to as Hemoglobin ε. Chromosomal abnormalities can lead to a delay in switching from embryonic hemoglobin. Hemoglobin Gower 1 (also referred to