Hemoglobiinis

Hemoglobiinis, commonly referred to as hemoglobin, is the iron-containing protein in red blood cells that binds oxygen in the lungs and releases it in tissues, while also carrying carbon dioxide from tissues back to the lungs for exhalation. It contributes to maintaining acid–base balance and enables efficient oxygen transport through cooperative binding, responding to changes in pH and carbon dioxide levels.

In humans, the principal adult form is HbA, a tetramer composed of two alpha and two beta globin chains, each bound to a heme group containing iron(II). This arrangement enables reversible, cooperative binding of up to four oxygen molecules per hemoglobiinis molecule. Fetal hemoglobiinis (HbF) uses gamma chains and has higher oxygen affinity, facilitating transfer from mother to fetus. Other adult variants include HbA2 (alpha2 delta2) and a range of inherited or acquired abnormal hemoglobins.

Biosynthesis occurs during erythropoiesis in the bone marrow; iron availability and proper heme synthesis are essential. Mature red blood cells containing hemoglobiinis circulate for about 120 days before being removed by the spleen or liver when damaged.

Clinical relevance: low levels of hemoglobiinis indicate anemia; elevated levels can reflect polycythemia. Mutations in globin genes cause disorders such as sickle cell disease (HbS) and various thalassemias. Methemoglobinemia and other abnormal forms can impair oxygen delivery. Hemoglobiinis measurements are widely used in clinical testing, and HbA1c serves as a marker of long-term glucose exposure in diabetes management.