respiratory pigment
Quick Summary
Respiratory pigments are protein molecules, often containing metal, that are crucial for transporting oxygen in the blood of many animals. These pigments significantly increase the blood's oxygen-carrying capacity, enabling more active organisms to meet their higher oxygen demands.12
The most common respiratory pigment is hemoglobin, a red protein found in the red blood cells of vertebrates and in the blood of most invertebrates. Hemoglobin binds reversibly with oxygen, turning bright red when oxygenated and purplish-blue when reduced. Each hemoglobin molecule consists of four heme groups, each containing an iron atom that binds to an oxygen molecule.13
Other respiratory pigments include green chlorocruorins and violet hemerythrins, both iron-containing proteins, and copper-containing hemocyanins, which turn blue when oxygenated. These pigments not only transport oxygen but can also store it for periods of low oxygen availability and help buffer blood pH.1
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