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Biochemistry/Respiratory Pigments
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In humans, these pigments include hemoglobin and myoglobin, the latter is present in red muscle fibers. Hemoglobin is a coordination compound of iron. It had attachment sites for gases, namely oxygen and carbon dioxide. Its reactivity depends upon partial pressure of these gases. The presence of heme makes it appear red colored. Myoglobin is present in muscles to make available extra oxygen.