Hämoglobins

Hämoglobins are a group of metalloproteins found in the red blood cells of vertebrates and some invertebrates, responsible for transporting oxygen from the lungs or gills to tissues and returning carbon dioxide back. The most well-known form, hemoglobin, is a tetrameric protein composed of four polypeptide chains: two alpha chains and two beta chains in adults, each containing a heme group with an iron atom that binds oxygen reversibly. This binding is cooperative, meaning the affinity for oxygen increases with each molecule bound, facilitating efficient oxygen transport.

Hemoglobins vary across species and can be classified based on their structure and function. For example, myoglobin, found in muscle tissues, stores oxygen for later use during periods of high demand. Invertebrates possess diverse hemoglobins, such as those in earthworms and certain mollusks, which may be extracellular or intracellular and sometimes contain multiple subunits. Some hemoglobins also bind other gases like carbon monoxide or nitric oxide, influencing physiological processes beyond oxygen transport.

Hemoglobin disorders arise from genetic mutations affecting its structure or function. Common examples include sickle cell anemia, caused by a single amino acid substitution in the beta-globin chain, and thalassemias, which result from reduced synthesis of one or more globin chains. These conditions impair oxygen-carrying capacity and can lead to severe health complications.

Hemoglobins play a critical role in respiratory physiology, and their study provides insights into evolutionary adaptations, disease mechanisms, and potential therapeutic targets. Research continues to explore their structural diversity, functional variations, and clinical implications across different organisms.