Haemocyanin

Haemocyanin (or hemocyanin) is a protein which transports oxygen in the bodies of some invertebrates. Their active centre has two copper atoms which reversibly bind a single oxygen molecule (O2). Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not bound to blood cells. The molecules are carried in the haemolymph. 

Hemocyanins are found only in the Mollusca and Arthropoda. Burmester T. 2001. Molecular evolution of the arthropod hemocyanin superfamily. Mol. Biol. Evol. 18 (2): 184–195. Voit R. et al 2000. Complete sequence of the 24-mer hemocyanin of the tarantula Eurypelma californicum. Structure and intramolecular evolution of the subunits. J. Biol. Chem. 275 (50): 39339–44.  However, the molecule is used only in a few insects. This is because insects evolved another system: the direct transfer of oxygen to tissues by a system of tubes called trachea. This delivers oxygen directly to the wing muscles and other organs.

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Category:Copper compounds
Category:Physiology
Category:Invertebrates
Category:Proteins