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In these tissues, hemoglobin absorbs unneeded oxygen as an antioxidant, and regulates iron metabolism. [12] Excessive glucose in the blood can attach to hemoglobin and raise the level of hemoglobin A1c. [13] Hemoglobin and hemoglobin-like molecules are also found in many invertebrates, fungi, and plants. [14]
Binding of oxygen to a heme prosthetic group. Heme (American English), or haem (Commonwealth English, both pronounced /hi:m/ HEEM), is a ring-shaped iron-containing molecular component of hemoglobin, which is necessary to bind oxygen in the bloodstream. It is composed of four pyrrole rings with 2 vinyl and 2 propionic acid side chains. [1]
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).
When hemoglobin is not attached to oxygen (and is then called deoxyhemoglobin), the Fe 2+ ion at the center of the heme group (in the hydrophobic protein interior) is in a high-spin configuration. It is thus too large to fit inside the porphyrin ring, which bends instead into a dome with the Fe 2+ ion about 55 picometers above it. In this ...
Hemoglobin A (HbA), also known as adult hemoglobin, hemoglobin A1 or α 2 β 2, is the most common human hemoglobin tetramer, accounting for over 97% of the total red blood cell hemoglobin. [1] Hemoglobin is an oxygen-binding protein, found in erythrocytes , which transports oxygen from the lungs to the tissues. [ 2 ]
Each hemoglobin molecule carries four heme groups; hemoglobin constitutes about a third of the total cell volume. Hemoglobin is responsible for the transport of more than 98% of the oxygen in the body (the remaining oxygen is carried dissolved in the blood plasma). The red blood cells of an average adult human male store collectively about 2.5 ...
The average red blood cell contains 250 million hemoglobin molecules. [7] Hemoglobin contains a globin protein unit with four prosthetic heme groups (hence the name heme-o-globin); each heme is capable of reversibly binding with one gaseous molecule (oxygen, carbon monoxide, cyanide, etc.), [8] therefore a typical red blood cell may carry up to one billion gas molecules.
After being carried in blood to a body tissue in need of oxygen, O 2 is handed off from the heme group to monooxygenase, an enzyme that also has an active site with an atom of iron. [9] Monooxygenase uses oxygen for many oxidation reactions in the body. Oxygen that is suspended in the blood plasma equalizes into the tissue according to Henry's law.