Haemoglobin

Definition: Haemoglobin

Haemoglobin

Noun

1. A hemoprotein composed of globin and heme that gives red blood cells their characteristic color; function primarily to transport oxygen from the lungs to the body tissues; "fish have simpler hemoglobin than mammals".

Date "haemoglobin" was first used in popular English literature: sometime before 1887. (references)

Synonym: Haemoglobin

Synonym: hemoglobin (n). (additional references)

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Specialty Definition: Hemoglobin

(From Wikipedia, the free Encyclopedia)

Haemoglobin (or hemoglobin) is the iron-containing oxygen-transport metalloprotein in the red cells of the blood in mammals and other animals. The molecule is mostly protein: mutations in the gene for the haemoglobin protein result in the hereditary diseases sickle cell anaemia and thalassaemia, as well as a group of diverse but rare diseases called hemoglobinopathies.

Structure

At the core of the molecule is a heterocyclic ring, known as a porphyrin which holds an iron atom; this iron atom is the site of oxygen binding. An iron containing porphyrin is termed a heme. The name hemoglobin is the concatenation of heme and globin, a globin being a generic term for a globular protein. Since a single subunit of hemoglobin is, in fact, made of a heme imbedded in a globular protein, the name makes sense. There are a number of heme containing proteins. Hemoglobin is by far the most famous.

In adult humans, hemoglobin is a tetramer, consisting of two alpha and two beta subunits noncovalently bound. The subunits are structurally similar and about the same size. Each subunit has a molecular weight of about 16,000, for a total molecular weight in the tetramer of about 64,000. Each subunit of hemoglobin contains a single heme, so that the overall binding capacity of adult human hemoglobin for oxygen is four oxygen molecules:

Stepwise Reaction:

Hb + O₂ <-> HbO₂
HbO₂ + O₂ <-> Hb(O₂)₂
Hb(O₂)₂ + O₂ <-> Hb(O₂)₃
Hb(O₂)₃ + O₂ <-> Hb(O₂)₄

Summary Reaction:

Hb + 4O₂ -> Hb(O₂)₄

A structure of deoxy human hemoglobin is given by PDB 1A3N.

Binding of ligands

In the tetrameric form of normal adult hemoglobin, the binding of oxygen is a cooperative process, with the binding affinity of hemoglobin for oxygen affected by the oxygen saturation of the molecule. As a consequence, the oxygen binding curve of hemoglobin is sigmoidal, or 'S' shaped, as opposed to the normal hyperbolic (noncooperative) curve.

Hemoglobin's affinity for oxygen is decreased in the presence of carbon dioxide and at lower pH. Carbon dioxide reacts with water to give bicarbonate, via the reaction:

CO₂ + H₂O <-> HCO₃^- + H⁺

So blood with high carbon dioxide levels is also lower in pH. Hemoglobin can bind protons and carbon dioxide which causes a conformational change in the protein and facilitates the release of oxygen. Protons bind a various places along the protein and carbon dioxide binds at the alpha-amino group forming carbamate. Conversely, when the carbon dioxide levels in the blood decrease (i.e. around the lungs), carbon dioxide is released, increasing the oxygen affinity of the protein. This control of hemoglobin's affinity for oxygen by the binding and release of carbon dioxide is known as the Bohr effect.

The binding of oxygen as well is affected by molecules such as 2,3-diphosphoglycerate, which lowers the affinity of hemoglobin for oxygen. In people acclimated to high altitudes, the concentration of 2,3-diphosphoglycerate in the blood is increased, which allows these individuals to deliver a larger amount of oxygen to tissues under conditions of lower oxygen tension. This phenomenon, where molecule Y affects the binding of molecule X to a transport molecule H, is called a heterotropic allosteric effect.

Degradation of haemoglobin

When red cells reach the end of their life, they are broken down, and the haemoglobin molecule broken up and the iron recycled. When the porphyrin ring is broken up, the fragments are normally secreted in the bile by the liver. There is a a group of genetic disorders, known as porphyrias that are characterized by errors in metabolic pathways of heme synthesis.
King George III of the United Kingdom was probably the most famous porphyria sufferer.

The major final product of heme degradation is bilirubin. Increased levels of this chemical are detected in the blood if red cells are being destroyed more rapidly.

Similar proteins

Finally, it should be noted that hemoglobin is by no means unique. There are a variety of oxygen transport proteins throughout the animal (and plant!) kingdom. Muscle tissue contains the hemoglobin-like pigment named myoglobin. Some marine invertebrates and one species of annelid use an iron containing non-heme protein called a hemerythrin. Many annelids, including the earthworm, use an oxygen transport protein called an erythrocruorin. Many arthropods and molluscs use a class of compounds, the hemocyanins, that contain copper instead of iron. And in leguminous plants, such as alfalfa, the nitrogen fixing bacteria of the roots are protected by leghemoglobin, a protein synthesized by the combined action of plant and bacterium.

Crosswords: Haemoglobin

English words defined with "haemoglobin": Cruorin. (references)

Specialty definitions using "haemoglobin": 2,3-diphosphoglycerate ♦ bacillary haemoglobinuria, bacillary hemoglobinuria ♦ Clostridium haemolyticum infection ♦ iron deficiency ♦ methaemoglobinaemia. (references)

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Commercial Usage: Haemoglobin

Domain	Title
Books	Haemoglobin (reference) Haemoglobin, isoenzymes and tissue differentiation (reference) Human haemoglobin variants and their characteristics (reference) Regulation of haemoglobin synthesis (reference) Science Is Not a Quiet Life: Unravelling the Atomic Mechanism of Haemoglobin (reference) (more book examples)
Source: compiled by the editor from various references; see credits.

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Usage Frequency: Haemoglobin

"Haemoglobin" is generally used as a noun (singular) -- approximately 100.00% of the time. "Haemoglobin" is used about 302 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted)

Parts of Speech	Percent	Usage per 100 Million Words	Rank in English
Noun (singular)	100%	302	16,684

Source: compiled by the editor from several corpora; see credits.

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Expressions: Haemoglobin

Hyphenated Usage
	Beginning with "haemoglobin": haemoglobin-carrying, haemoglobin-measuring, haemoglobin-plus.
Source: compiled by the editor from various references; see credits.

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Frequency of Internet Keywords: Haemoglobin

The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com.

Expression	Frequency per Day
haemoglobin	29
haemoglobin a1c	5
haemoglobin low	5
glycated haemoglobin	3
haemoglobin level	2
Source: compiled by the editor from various references; see credits.

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Modern Translations: Haemoglobin

Language		Translations for "haemoglobin"; alternative meanings/domain in parentheses.
Albanian		hemoglobinë (hemoglobin). (various references)

Arabic		‏هموجلوبين بروتين (hemoglobin). (various references)

Bulgarian		хемоглобин (hemoglobin). (various references)

Chinese		血红蛋白 (hemoglobin). (various references)

Czech		hemoglobin. (various references)

Danish		haemoglobin (blood chromoproteid), blodchromoproteid (blood chromoproteid). (various references)

Dutch		hemoglobine (blood chromoproteid). (various references)

Finnish		hemoglobiinin valmistumista haittaava poikkeavuus (anomaly affecting the synthesis of haemoglobin), verenpunan elektroforeesi (haemoglobin electrophoresis, hemoglobin electrophoresis). (various references)

French		hémoglobine. (various references)

German		HB, Haemoglobin (blood chromoproteid), Hämoglobin (hemoglobin), Chromoproteid des Blutes (blood chromoproteid). (various references)

Greek		αιμοσφαιρίνη (hemoglobin). (various references)

Hebrew		�"מו�'לובין. (various references)

Hungarian		hemoglobin (hemoglobin), vörös vértestecskék, vérfesték. (various references)

Italian		emoglobina (blood chromoproteid, hemoglobin). (various references)

Japanese Kanji		血色� . (various references)

Japanese Katakana		けっしきそ. (various references)

Korean		헤모글로빈 (hemoglobin). (various references)

Pig Latin		aemoglobinhay.(various references)

Portuguese		hemoglobina (blood chromoproteid, haemophilia, hemophilia), hematoma (black mark, blue mark, haematoma, hemisphere, macula caerulea, macula cerulea), cromoproteída do sangue (blood chromoproteid). (various references)

Romanian		hemoglobinã (hemoglobin). (various references)

Russian		гемоглобин (hemoglobin). (various references)

Serbo-Croatian		hemoglobin (hemoglobin). (various references)

Spanish		hemoglobina (blood chromoproteid, hemoglobin). (various references)

Swedish		hemoglobin (hemoglobin). (various references)

Thai		ฮีโมโกลบิน (hemoglobin). (various references)

Turkish		hemoglobin (hemoglobin). (various references)

Ukranian		гемоглобін (hemoglobin). (various references)

Vietnamese		Hemoglobin (hemoglobin). (various references)
Source: compiled by the editor from various translation references.

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Rhyming with "Haemoglobin"

Words rhyming with "haemoglobin" (pronounced 'H[ae]m`o*glo"bin'): Aubin, Bilirubin, Bobbin, Calumbin, Chrysarobin, hemoglobin, Indirubin, Methaemoglobin, Nubbin, Rabbin, Rubin, Sinalbin, Sorbin, thrombin. (additional references)

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Anagrams: Haemoglobin

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "a-b-e-g-h-i-l-m-n-o-o"
	-1 letter: hemoglobin.
	-3 letters: blooming, bohemian, bonhomie, hooligan.
	-4 letters: ambling, beaming, begloom, begonia, blaming, bohemia, bologna, booming, geminal, goombah, halogen, haloing, hambone, healing, helming, hemiola, hobnail, hoboing, hogmane, ignoble, lambing, loaming, looming, manhole, minable, oinomel.
	-5 letters: abloom, albino, anomie, bagmen, bagnio, baling, bangle, belong, bemoan, biogen, blooie, boogie, booing, eloign, emboli, enhalo, enigma, eolian, gabion, gaboon, gamble, gambol, gamine, genial, gimbal, glioma, globin, goalie, goblin, goonie, habile, haeing, haemin, haling, hiemal, hoagie, hoeing, holing, homage, homing, hoolie, inhale, lagoon, lambie, laming, legion, legman, linage, lingam, logion, lomein, looing, malign, maline, mangel, mangle, menial, milage, milneb, mingle, mobile, moline, mongoe, mongol, mooing, moolah, nimble, obelia, oblige, oblong, ohmage, oilman, oilmen, oohing.
	Words containing the letters "a-b-e-g-h-i-l-m-n-o-o"
	+3 letters: hemoglobinuria.
	+4 letters: hemoglobinurias.
	+5 letters: hemoglobinopathy.
Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro.