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Hemoglobin, erythrocruorin, and chlorocruorin are all globins, iron-heme proteins with a common core. Their color comes from the absorption spectra of heme with Fe 2+. Erythrocruorin and chlorocruorin are closely related giant globins found used by some invertebrates. Chlorocruorin has a special heme group, giving it different colors.
Roughly 5 grams of iron are present in the human body and is the most abundant trace metal. [1] It is absorbed in the intestine as heme or non-heme iron depending on the food source. Heme iron is derived from the digestion of hemoproteins in meat. [4] Non-heme iron is mainly derived from plants and exist as iron(II) or iron(III) ions. [4]
The heme iron serves as a source or sink of electrons during electron transfer or redox chemistry. In peroxidase reactions, the porphyrin molecule also serves as an electron source, being able to delocalize radical electrons in the conjugated ring. In the transportation or detection of diatomic gases, the gas binds to the heme iron.
Iron-binding proteins are carrier proteins and metalloproteins that are important in iron metabolism [1] and the immune response. [2] [3] Iron is required for life.Iron-dependent enzymes catalyze a variety of biochemical reactions and can be divided into three broad classes depending on the structure of their active site: non-heme mono-iron, non-heme diiron , or heme centers. [4]
Hemin is protoporphyrin IX containing a ferric iron (Fe 3+) ion with a coordinating chloride ligand. Chemically, hemin differs from the related heme-compound hematin chiefly in that the coordinating ion is a chloride ion in hemin, whereas the coordinating ion is a hydroxide ion in hematin. [ 2 ]
Two globin chains that have heme groups combine to form hemoglobin. One of the chains is an alpha chain and the other is a non-alpha chain. Non-alpha chain nature in hemoglobin molecules varies due to different variables. Fetuses have a non-alpha chain called gamma and after birth it is then called beta. The beta chain will pair with the alpha ...
However, the complex of oxygen with heme iron is diamagnetic, whereas both oxygen and high-spin iron(II) are paramagnetic. Experimental evidence strongly suggests heme iron is in the iron(III) oxidation state in oxyhemoglobin, with the oxygen existing as superoxide anion (O 2 •−) or in a covalent charge-transfer complex. [58]
The structure of hemoglobin.The heme cofactor, containing the metal iron, shown in green.. Metalloprotein is a generic term for a protein that contains a metal ion cofactor. [1] [2] A large proportion of all proteins are part of this category.