Diff: Haemoglobin
Comparing revision #1 (2023-06-10 00:42:47) with revision #2 (2026-06-22 09:09:10).
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'''Haemoglobin''' is an iron-containing protein in red blood cells that carries oxygen from the lungs to tissues. It also helps carry carbon dioxide and contributes to blood buffering. Haemoglobin gives red blood cells much of their colour and is central to the diagnosis of [[Anaemia|anaemia]] and many inherited blood disorders. |
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Hemoglobin is a protein found in red blood cells (erythrocytes) that plays a crucial role in transporting oxygen throughout the body. It is responsible for binding to oxygen in the lungs and releasing it to the tissues. |
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The abbreviation '''Hb''' is commonly used in medicine and laboratory reports. |
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== Structure == |
== Structure == |
Hemoglobin is composed of four protein subunits, each known as a globin chain, and a heme group. In adults, there are two types of globin chains: alpha and beta. The combination of these chains determines the specific type of hemoglobin present. |
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The heme group, located within each globin chain, contains iron atoms that bind to oxygen molecules. This allows hemoglobin to effectively transport oxygen from the lungs to the tissues. |
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== Types of Hemoglobin == |
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There are several types of hemoglobin, each with distinct properties and functions: |
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Adult haemoglobin is mainly haemoglobin A. It is made from four protein subunits: two alpha-globin chains and two beta-globin chains. Each chain is attached to a haem group containing iron. Each haem group can bind one oxygen molecule, so one haemoglobin molecule can carry up to four oxygen molecules. |
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# Adult Hemoglobin (HbA): The predominant hemoglobin in adults, consisting of two alpha chains and two beta chains. |
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# Fetal Hemoglobin (HbF): Present in the fetus, HbF has a higher affinity for oxygen than adult hemoglobin. It consists of two alpha chains and two gamma chains. |
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# Embryonic Hemoglobin (HbE): Found in the embryonic stage, HbE consists of two zeta chains and two epsilon chains. |
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# Other Hemoglobin Variants: Numerous genetic variations can result in different forms of hemoglobin, such as HbS (sickle hemoglobin) and HbC (hemoglobin C). These variants can lead to specific blood disorders when inherited. |
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MedlinePlus Genetics describes beta-globin as a subunit of haemoglobin and notes that adult haemoglobin typically contains two beta-globin subunits and two alpha-globin subunits. |
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== Function == |
== Function == |
The primary function of hemoglobin is to transport oxygen from the lungs to the body's tissues and carry carbon dioxide back to the lungs for elimination. This oxygen-binding capability is crucial for cellular respiration, providing oxygen to cells for energy production. |
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Haemoglobin binds oxygen in the lungs, where oxygen concentration is high, and releases oxygen in tissues, where oxygen concentration is lower. This allows red blood cells to deliver oxygen throughout the body. |
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Hemoglobin's ability to bind and release oxygen is influenced by several factors, including partial pressure of oxygen, pH levels, and the presence of other molecules like carbon dioxide and hydrogen ions. |
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Haemoglobin also helps carry carbon dioxide from tissues back to the lungs and helps buffer blood pH. Its oxygen-binding behaviour changes with acidity, carbon dioxide, temperature, and 2,3-bisphosphoglycerate, allowing oxygen delivery to increase in active tissues. |
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== Hemoglobin Disorders == |
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Several genetic disorders can affect the production or structure of hemoglobin, leading to abnormal functioning or reduced oxygen-carrying capacity. Examples of hemoglobin disorders include: |
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== Main Forms == |
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Important forms include: |
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* Sickle Cell Disease: A condition in which abnormal hemoglobin causes red blood cells to become sickle-shaped, leading to various complications. |
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* Thalassemia: A group of inherited disorders characterized by reduced production of specific globin chains, resulting in anemia. |
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* Hemoglobinopathies: Genetic variations in hemoglobin structure that can cause conditions such as hemoglobin C disease, hemoglobin E disease, and others. |
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* '''Haemoglobin A''': the main adult form, made from two alpha and two beta chains. |
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* '''Haemoglobin A2''': a smaller adult fraction, made from alpha and delta chains. |
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* '''Fetal haemoglobin''': the main fetal form, made from alpha and gamma chains. It binds oxygen more strongly than adult haemoglobin, helping oxygen transfer from mother to fetus. |
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* '''Variant haemoglobins''': inherited forms such as haemoglobin S, C, and E. |
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Different forms can be measured by haemoglobinopathy screening, electrophoresis, high-performance liquid chromatography, or related laboratory methods. |
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== Measurement == |
== Measurement == |
Hemoglobin levels can be measured through a blood test called a complete blood count (CBC). The results provide valuable information about an individual's red blood cell count and hemoglobin concentration. |
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Haemoglobin concentration is usually measured as part of a full blood count. The result helps assess anaemia, polycythaemia, bleeding, nutritional deficiency, chronic disease, and response to treatment. |
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Normal hemoglobin levels vary depending on factors such as age, sex, and altitude. In adults, the typical range is 12 to 16 grams per deciliter (g/dL) for females and 13.5 to 17.5 g/dL for males. |
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Interpretation depends on age, sex, pregnancy, altitude, hydration, smoking, medical history, and laboratory reference ranges. A low haemoglobin result is not a diagnosis by itself. The cause must be investigated. |
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== Disorders == |
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Haemoglobin disorders include: |
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* [[Sickle Cell Disease|Sickle cell disease]], usually caused by haemoglobin S. |
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* [[Thalassaemia]], caused by reduced production of alpha or beta globin chains. |
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* Haemoglobin C disease. |
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* Haemoglobin E disease. |
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* Methaemoglobinaemia, where haem iron is in a form that cannot carry oxygen effectively. |
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These disorders can cause anaemia, pain crises, jaundice, enlarged spleen, pregnancy risk, stroke risk, infection risk, iron overload, or other complications, depending on the condition. |
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== Iron and Haem == |
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Iron is essential for haemoglobin function because oxygen binds to iron in the haem group. Iron deficiency can reduce haemoglobin production and cause iron deficiency anaemia. |
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Too much iron can also be harmful. People receiving repeated transfusions, such as some patients with thalassaemia major, may develop iron overload and need chelation treatment. |
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== See Also == |
== See Also == |
* [[Red Blood Cells]] |
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* [[Anaemia]] |
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* [[Thalassaemia]] |
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* [[Sickle Cell Disease]] |
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* [[Red Blood Cells]] - Learn about the cells responsible for carrying oxygen and nutrients throughout the body. |
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* [[Anemia]] - Explore a condition characterized by a deficiency of healthy red blood cells or hemoglobin. |
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== References == |
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* [https://medlineplus.gov/genetics/gene/hbb/ MedlinePlus Genetics: HBB gene] |
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* [https://medlineplus.gov/blood.html MedlinePlus: Blood] |
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* [https://www.nhs.uk/conditions/thalassaemia/ NHS: Thalassaemia] |
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* [https://www.nhsinform.scot/illnesses-and-conditions/nutritional/iron-deficiency-anaemia/ NHS inform: Iron deficiency anaemia] |
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[[Category:Medicine]] |
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[[Category:Haematology]] |
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[[Category:Biochemistry]] |