Role of Respiratory Pigments in Gaseous Exchange
RESPIRATORY PIGMENTS
Colored, metal-containing proteins that combine reversibly with oxygen, found in the body fluids or tissues of multi-cellular invertebrate animals and microorganisms. The role of these pigments is primarily to aid in the transport of molecular oxygen. Thus they are distinguished from respiratory enzymes, which are concerned with the metabolic consumption of oxygen. Four distinctly colored groups of respiratory pigments exist among invertebrates: hemoglobins (purple, become orange-red with oxygen), chlorocruorins (green, become red with oxygen), hemocyanins (colorless, become blue with oxygen), and hemerythrins (colorless, become red with oxygen). Formerly, invertebrate hemoglobins were called erythrocruorins to distinguish them from functionally similar yet structurally distinct pigments of vertebrate bloods.
1. HEMOCYANINS : Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule (O2). Oxygenation causes a color change between the colorless deoxygenated form and the blue oxygenated form. Hemocyanins carry oxygen in the hemolymph of most molluscs, and some arthropods, including the horseshoe crab, Limulus polyphemus. They are second only to hemoglobin in frequency of use as an oxygen transport molecule. Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not bound to blood cells but are instead suspended directly in the hemolymph.
Species using hemocyanin for oxygen transportation are commonly crustaceans living in cold environments with low oxygen pressure. Under these circumstances hemoglobin oxygen transportation is less efficient than hemocyanin oxygen transportation.
Hemocyanins are one-fourth as efficient as hemoglobin at transporting oxygen per amount of blood. Hemocyanin is made of many individual subunit proteins, each of which contains two copper atoms and can bind one oxygen molecule (O2). Because of the large size of
Colored, metal-containing proteins that combine reversibly with oxygen, found in the body fluids or tissues of multi-cellular invertebrate animals and microorganisms. The role of these pigments is primarily to aid in the transport of molecular oxygen. Thus they are distinguished from respiratory enzymes, which are concerned with the metabolic consumption of oxygen. Four distinctly colored groups of respiratory pigments exist among invertebrates: hemoglobins (purple, become orange-red with oxygen), chlorocruorins (green, become red with oxygen), hemocyanins (colorless, become blue with oxygen), and hemerythrins (colorless, become red with oxygen). Formerly, invertebrate hemoglobins were called erythrocruorins to distinguish them from functionally similar yet structurally distinct pigments of vertebrate bloods.
1. HEMOCYANINS : Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule (O2). Oxygenation causes a color change between the colorless deoxygenated form and the blue oxygenated form. Hemocyanins carry oxygen in the hemolymph of most molluscs, and some arthropods, including the horseshoe crab, Limulus polyphemus. They are second only to hemoglobin in frequency of use as an oxygen transport molecule. Unlike the hemoglobin in red blood cells found in vertebrates, hemocyanins are not bound to blood cells but are instead suspended directly in the hemolymph.
Species using hemocyanin for oxygen transportation are commonly crustaceans living in cold environments with low oxygen pressure. Under these circumstances hemoglobin oxygen transportation is less efficient than hemocyanin oxygen transportation.
Hemocyanins are one-fourth as efficient as hemoglobin at transporting oxygen per amount of blood. Hemocyanin is made of many individual subunit proteins, each of which contains two copper atoms and can bind one oxygen molecule (O2). Because of the large size of