User:Tuor~enwiki/Sandbox/Biological oxygen-binding proteins

Throughout the animal kingdom, several structures are used for the transportation of oxygen to organs. Among these are Hemoglobin, Hemocyanin, Chlorocruorin, Vanadium chromagen, copper-based porphyrin, manganese-based porphyrin pinnaglobin, as well as several conjectural types incorporating cobalt and vanadium.

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Myoglobin: Found in the muscle tissue of many vertebrates including humans (gives muscle tissue a distinct red or dark gray color). Is very similar to hemoglobin in structure and sequence, but is not arranged in tetramers, it is a monomer and lacks cooperative binding and is used to store oxygen rather than transport it.

Hemocyanin: Second most common oxygen transporting protein found in nature. Found in the blood of many arthropods and molluscs. Uses copper prosthetic group instead of iron heme groups and is blue in color when oxygenated.

Hemerythrin: Some marine invertebrates and a few species of annelid use this iron containing non-heme protein to carry oxygen in their blood. Appears pink/violet when oxygenated, clear when not.

Chlorocruorin: Found in many annelids, and is very similar to Erythrocruorin, but the heme group is significantly different in structure. Appears green when deoxygenated and red when oxygenated.

Vanabins: Also known as Vanadium Chromagen are found in the blood of Sea squirt and are hypothesised to use the rare metal Vanadium as its oxygen binding prosthetic group, but this hypothesis is unconfirmed.

Erythrocruorin: Found in many annelids, including earthworms. Giant free-floating blood protein, contains many dozens even hundreds of Iron heme containing protein subunits bound together into a single protein complex with a molecular masses greater than 3.5 million daltons.

Pinnaglobin: Only seen in the mollusk Pinna squamosa. Brown manganese-based porphyrin protein. Leghemoglobin: In leguminous plants, such as alfalfa or soybeans, the nitrogen fixing bacteria in the roots are protected from oxygen by this iron heme containing, oxygen binding protein.