Translations:Hämoglobin/1/en

A blood pigment consisting of globin as a protein component and the iron-containing prosthetic group Hematin as the active centre of oxygen binding. Each erythrocyte consists of 90% haemoglobin and thus contains about 250 million haemoglobin molecules. Each haemoglobin molecule consists of four subunits, each containing a haem group. An iron ion is bound in the centre of the heme group. This iron exerts a strong attraction, so-called affinity, on oxygen, whereby the oxygen (or one oxygen molecule in each case) is bound to the haemoglobin. Hemoglobin binds oxygen (O₂) under the high partial pressure of inhalation air in the lungs and turns light red (oxyhaemoglobin), under the low partial pressure in peripheral tissues due to oxygen consumption, oxyhaemoglobin releases oxygen and turns dark red (reduced hemoglobin).

This results in the different colouring of arterial and venous blood, as well as the reddish colour of skin with good blood circulation and the bluish colour in case of poor oxygen saturation of the arterial blood. After bicarbonate, hemoglobin forms the most important buffer in the blood to keep its pH constant. Under a purple discoloration of the blood pigment, carbon monoxide (CO) displaces the oxygen from the haemoglobin as a result of higher binding strength, so that it can no longer be transported into the tissue. The resulting tissue nitrogenization causes the toxicity of carbon monoxide.