Hem

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Hemoglobin (or haemoglobin and abbreviated as Hb or Hgb) is an iron-containing oxygen-transport metaloprotein in the red blood cells of almost all vertebrates (the exception being the fish family Channichthyidae) as well as the tissues of some invertebrates. Hemoglobin in the blood carries oxygen from the lungs or gills to the rest of the body (such as its muscles and organs). It then aids in the transportation of carbon dioxide back to the lungs to be exhaled.

Structure

Hemoglobin is a quaternary structured protein consisting of four polypeptide chains (two alpha and two beta chains that are identical within themselves but different from each other). Each chain is attached to a heme group composed of porphyrin (an organic ring-like structure) bound to an iron atom. These iron atoms bind to oxygen molecules in the lungs and carry them throughout the body. The binding of oxygen causes a conformational change in the protein, which facilitates the delivery of oxygen to tissue.

Function

The primary function of hemoglobin is to transport oxygen from the lungs to the body's tissues, enabling aerobic respiration to provide energy to power the functions of the organism. Hemoglobin also plays a role in the transport of carbon dioxide, a waste product of metabolism, from the tissues back to the lungs where it can be exhaled. The protein's ability to bind oxygen is regulated by the concentration of carbon dioxide, the pH level (known as the Bohr effect), and the concentration of 2,3-Bisphosphoglycerate (2,3-BPG) in the red blood cells.

Types of Hemoglobin

There are several types of hemoglobin, including:

• Hemoglobin A (HbA) - the most common type found in adults.
• Hemoglobin F (HbF) - fetal hemoglobin, which has a higher affinity for oxygen than adult hemoglobin.
• Hemoglobin A2 (HbA2) - a minor component of adult hemoglobin.
• Hemoglobin S (HbS) - a variant associated with sickle cell anemia, a genetic disorder that results in abnormal hemoglobin molecules that can lead to various health complications.

Genetics

The genes responsible for the production of the alpha and beta chains of hemoglobin are located on different chromosomes (the alpha chains on chromosome 16 and the beta chains on chromosome 11). Mutations in these genes can lead to hemoglobinopathies, which are disorders caused by abnormalities in the structure or production of hemoglobin. Examples include sickle cell anemia, thalassemia, and methemoglobinemia.

Clinical Significance

Abnormalities in hemoglobin levels can indicate various medical conditions. Low hemoglobin levels (anemia) can result in fatigue, weakness, and shortness of breath. High levels (polycythemia) can increase the risk of thrombosis. Hemoglobin levels are measured as part of a complete blood count (CBC) test, which is a common diagnostic tool in medicine.

History

The study of hemoglobin has a long history, with significant contributions from multiple scientists over the years. The discovery of the heme structure by Hans Fischer in 1934 earned him the Nobel Prize in Chemistry.