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Hemoglobin in the blood carries oxygen from the respiratory organs (lungs or gills) to the other tissues of the body, where it releases the oxygen to enable aerobic respiration which powers an animal's metabolism. A healthy human has 12 to 20 grams of hemoglobin in every 100 mL of blood. Hemoglobin is a metalloprotein, a chromoprotein, and ...
The molecular mechanism behind this effect is the steric organization of the globin chain; a histidine residue, located adjacent to the heme group, becomes positively charged under acidic conditions (which are caused by dissolved CO 2 in working muscles, etc.), releasing oxygen from the heme group.
Heme B or haem B (also known as protoheme IX) is the most abundant heme. [1] Hemoglobin and myoglobin are examples of oxygen transport proteins that contain heme B. The peroxidase family of enzymes also contain heme B.
Hemoglobin has an oxygen binding capacity between 1.36 and 1.40 ml O 2 per gram hemoglobin, [23] which increases the total blood oxygen capacity seventyfold, [24] compared to if oxygen solely were carried by its solubility of 0.03 ml O 2 per liter blood per mm Hg partial pressure of oxygen (about 100 mm Hg in arteries). [24]
Aluminium, the third most common element in the Earth's crust (after oxygen and silicon), serves no function in living cells, but is toxic in large amounts, depending on its physical and chemical forms and magnitude, duration, frequency of exposure, and how it was absorbed by the human body. [38] Transferrins can bind aluminium. [39]
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]
Histidine is a common ligand for many hemeproteins including hemoglobin and myoglobin. Heme A in the cytochrome a portion of cytochrome c oxidase, bound by two histidine residues (shown in pink) [6] An example of a metalloprotein that contains heme A is cytochrome c oxidase.
Biliverdin results from the breakdown of the heme moiety of hemoglobin in erythrocytes. Macrophages break down senescent erythrocytes and break the heme down into biliverdin along with hemosiderin, in which biliverdin normally rapidly reduces to free bilirubin. [1] [3] Biliverdin is seen briefly in some bruises as a green color.