hemoglobine

Hemoglobine, often written as hemoglobin in English, is a protein contained primarily in red blood cells that transports oxygen from the lungs to tissues and assists in the removal of carbon dioxide. In humans the principal adult form is HbA, a tetramer composed of two alpha globin and two beta globin chains. Each globin chain surrounds a heme group, a porphyrin ring with an iron atom that binds O2 reversibly.

Function and regulation: Hemoglobine binds oxygen in the lungs where oxygen tension is high and releases it in tissues with lower tension. In the opposite process, deoxygenated hemoglobine carries carbon dioxide back to the lungs, though most CO2 is transported as bicarbonate in plasma. Affinity for oxygen is modulated by pH (the Bohr effect), temperature, and allosteric effectors such as 2,3-bisphosphoglycerate (2,3-BPG).

Genetics and development: Globin genes are organized in clusters; alpha-like genes reside on chromosome 16 and beta-like genes on chromosome 11. Fetal hemoglobine (HbF, alpha2 gamma2) has higher O2 affinity and is gradually replaced by HbA after birth.

Clinical relevance: Hemoglobine concentration is a standard measure of red cell mass. Structural variants and imbalances, such as sickle hemoglobine (HbS) and various thalassemias, can impair oxygen transport and cause anemia or other circulatory problems.