Did you know that Peter Jackson before performing the Seigneurdes rings was a filmmaker at a very low budget gore? (See forexample " Braindead" or "Bad Taste" ...) Autrefilm well suited to our topic of the day: "Sweeney Todd the diaboliquebarbier of Fleet Street" by Tim Burton. And what about the series Dexter , where the main character is an expert analysis of bloodstains etégalement a serial killer. You guessed it, our topic today is the blood. Star of horror films, its bright red color makes enalerte our senses, and just to look the most sensitive (C'estd'ailleurs why the Orcs have black blood and not red in the Lord of the Rings : éviteainsi we ban the movie at least 12 years ...). But what is due cettecouleur so intense? And why not oxygenated blood veins is represented iltoujours darker or bluer than oxygenated blood desartères? 
blood with hemoglobin
What's the blood? Well mission centrifugal blood there are three fractions: plasma rather yellow is the liquid portion of blood, it is 55% of whole blood, platelets and white lesglobules (less than 1%) and finally the famous globulesrouges called erythrocytes in humans that correspond to 45% of total volume (PCV s'appelleégalement This percentage, an analysis blood).
These RBCs give blood its red color, this sontdes cells without nuclei and organelles practically, they contain a single protein pourl'essentiel: the famous hemoglobin . These sacsd'hémoglobine mission is to carry oxygen Entire organismegrâce this protein with remarkable properties (I'm sure all fans of the animated fameuxdessin " Once upon a time ... Life " remember).
[ RBCs in microscopieélectronique scanning (false color) and in the cartoon "Once upon a time ... Life "(Albert Barillé - 1987) .]
The structure of hemoglobin
The protein is composed of protein subunits 4sous, globins: two andtwo α β, each sub subunit is linked to groupof non-protein, heme, hence the name: "hemoglobin". This contains a heme iron atom which may seli with the oxygen molecule. Each million moléculesd'hémoglobine a red blood cell can carry 4 molecules dioxygène.L space reserved for oxygen, is not used to transport ledioxyde carbon (CO 2 ), cons by carbon monoxide (CO) is small enough to be fixed classical rayleigh quasi-irreversible at this site. As the place of O 2 is taken, lemanque oxygen soon becomes apparent even at low concentrations of CO ... This is the origin of carbon monoxide poisoning often linked to other boilers and stoves Devieux evil resolved.
[ Haemoglobin: a protein quaternary àstructure, that is to say composed of subunits. (2 α and 2 β) ]
A color variable according degréd'oxygénation.
In the absence of O 2 attached to hemoglobin, the iron atom II (ferrous) linked by a weak bond to an amino acid (histidine) is offset from the plane of the heme. It exceeds like it was drawn on the side by his association with histidine. Moreover, the distribution of electrons around the nucleus that the overall diameter of the atom is important. We're talking high-spin configuration. Conversely, when the oxygen binds to the iron atom on the side opposite to that of histidine, it takes a perfectly centered position relative to the plane of the heme, and its diameter is reduced: this is called configuration low spin. Cettesimple difference between the configuration and high spin low spin and the changes that accompany it, are sufficient to créerune significant difference in the absorption spectrum of the molecule, autrementdit, color. And oxyhemoglobin absorbs much less lescouleurs wave red (approx. 660nm) than deoxyhemoglobin, which therefore appears moinsrouge. Its appearance is duller, closer to the blue, and that is the reason decet conventional representation of non-oxygenated blood in blue and red sangoxygéné.
Above:
[A left : configuration and position of the iron atom in the plane of the heme in the case of oxygen. and deoxyhemoglobin.
A right : The absorption spectrum of oxygenated and non del'hémoglobine peroxide, measured at a TP physiologieanimale L3 (UPPA) . Deoxyhemoglobin (blue) absorbed much less in the red (660nm) and oxyhemoglobin (red).]
Hemoglobin, pigmentrespiratoire qualified because of his color, is not the only molecule to ensure cettefonction carrier O 2 in the animal world. In crustaceans and molluscs ouch, we find the hemocyanin, which has two atoms decuivre. The oxidized copper atom then gives a blue-green blood. Sansdoute orcs from Lord of the Rings did they also hémoglobinespécifique that does not use the iron ... I propose manganese, originally "tendencies black colorants.
To end on a note less trivial sachezque hemoglobin is an outstanding tool in molecular phylogeny lesgnathostomes (vertebrates with a jaw).
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