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Although the respiratory function of hemocyanin is similar to that of hemoglobin, there are a significant number of differences in its molecular structure and mechanism. Whereas hemoglobin carries its iron atoms in porphyrin rings (heme groups), the copper atoms of hemocyanin are bound as prosthetic groups coordinated by histidine residues.
Hemocyanin is a respiratory pigment that uses copper as its oxygen-binding molecule, as opposed to iron with hemoglobin. Hemocyanin is found in both arthropods and Mollusca , however it is thought that the molecule independently evolved in both phyla.
O 2-bound form of hemocyanin, the O 2 carrier for certain molluscs. These binding modes include μ 2-η 2,η 2-, μ 2-η 1,η 1-, and μ 2-η 1,η 2-. Depending on the degree of electron-transfer from the dimetal unit, these O 2 ligands can again be described as peroxo or superoxo. Hemocyanin is an O 2-carrier that
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 ...
It contains hemocyanin, a copper-based protein that turns blue when oxygenated, instead of the iron-based hemoglobin in red blood cells found in vertebrates, giving hemolymph a blue-green color rather than the red color of vertebrate blood. When not oxygenated, hemolymph quickly loses its color and appears grey.
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.
Unlike hemoglobin, most hemerythrins lack cooperative binding to oxygen, making it roughly 1/4 as efficient as hemoglobin. In some brachiopods though, hemerythrin shows cooperative binding of O 2. Cooperative binding is achieved by interactions between subunits: the oxygenation of one subunit increases the affinity of a second unit for oxygen.
In blood, the heme group of hemoglobin binds oxygen when it is present, changing hemoglobin's color from bluish red to bright red. [7] [8] Vertebrate animals use hemoglobin in their blood to transport oxygen from their lungs to their tissues, but other animals use hemocyanin (molluscs and some arthropods) or hemerythrin (spiders and lobsters).