Haemoglobin A

From WikiMD's Wellness Encyclopedia

Haemoglobin A (HbA) is the most common type of haemoglobin found in adults. It is a protein in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs. Haemoglobin A is composed of two alpha (α) and two beta (β) globin chains, forming a heterotetramer (α2β2). This composition distinguishes it from other forms of haemoglobin, such as haemoglobin F (HbF), which is predominant in the fetus and newborns, and haemoglobin A2 (HbA2), which is present in small amounts in adults.

Structure and Function[edit | edit source]

The structure of haemoglobin A is crucial for its function in oxygen transport. Each of the four globin chains in HbA contains a heme group, which is a porphyrin ring with an iron (Fe) atom at its center. This iron atom binds one molecule of oxygen, allowing each haemoglobin molecule to carry up to four oxygen molecules. The binding of oxygen causes a conformational change in the haemoglobin molecule, enhancing its ability to pick up more oxygen at high oxygen concentrations (in the lungs) and release oxygen at lower concentrations (in the tissues).

Genetics[edit | edit source]

The genes encoding the alpha and beta chains of haemoglobin A are located on different chromosomes. The alpha globin genes are found on chromosome 16, while the beta globin genes are located on chromosome 11. Mutations in these genes can lead to various haemoglobinopathies, such as sickle cell disease and beta-thalassemia, which affect the structure and function of haemoglobin.

Clinical Significance[edit | edit source]

Haemoglobin A levels are measured as part of a complete blood count (CBC) and are important in diagnosing and managing various medical conditions. Abnormal levels can indicate diseases such as anemia, polycythemia, and haemoglobinopathies. Additionally, the glycated haemoglobin (HbA1c) test, which measures the percentage of haemoglobin A that is bound to glucose, is used to monitor long-term glucose control in diabetes mellitus.

Variants[edit | edit source]

There are several genetic variants of haemoglobin A, resulting from mutations in the alpha or beta globin genes. These variants can affect the oxygen-carrying capacity and stability of the haemoglobin molecule. Some common variants include haemoglobin S (HbS), which causes sickle cell disease, and haemoglobin C (HbC), which can cause a mild form of haemolytic anemia.


WikiMD
Navigation: Wellness - Encyclopedia - Health topics - Disease Index‏‎ - Drugs - World Directory - Gray's Anatomy - Keto diet - Recipes

Search WikiMD

Ad.Tired of being Overweight? Try W8MD's physician weight loss program.
Semaglutide (Ozempic / Wegovy and Tirzepatide (Mounjaro / Zepbound) available.
Advertise on WikiMD

WikiMD's Wellness Encyclopedia

Let Food Be Thy Medicine
Medicine Thy Food - Hippocrates

Medical Disclaimer: WikiMD is not a substitute for professional medical advice. The information on WikiMD is provided as an information resource only, may be incorrect, outdated or misleading, and is not to be used or relied on for any diagnostic or treatment purposes. Please consult your health care provider before making any healthcare decisions or for guidance about a specific medical condition. WikiMD expressly disclaims responsibility, and shall have no liability, for any damages, loss, injury, or liability whatsoever suffered as a result of your reliance on the information contained in this site. By visiting this site you agree to the foregoing terms and conditions, which may from time to time be changed or supplemented by WikiMD. If you do not agree to the foregoing terms and conditions, you should not enter or use this site. See full disclaimer.
Credits:Most images are courtesy of Wikimedia commons, and templates Wikipedia, licensed under CC BY SA or similar.

Contributors: Prab R. Tumpati, MD