myoglobin

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myoglobin A globular protein occurring widely in muscle tissue as an oxygen carrier. It comprises a single polypeptide chain and a haem group, which reversibly binds a molecule of oxygen. This is only relinquished at relatively low external oxygen concentrations, e.g. during strenuous exercise when muscle oxygen demand outpaces supply from the blood. Myoglobin thus acts as an emergency oxygen store.

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myoglobin A haemoprotein, consisting of a single polypeptide chain surrounding a haem group, that is capable of reversibly binding oxygen. It has a higher affinity for oxygen than has haemoglobin and releases it only when the oxygen supply becomes limiting. Myoglobin is found in the muscles of vertebrates and certain invertebrates, where it serves to store oxygen.

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myoglobin (my-oh-gloh-bin) n. see myohaemoglobin.