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The Three Molecules of Life
The three molecules, Chlorophyll, Hemoglobin and Hemacyanin, are remarkably similar. All three are metalo-organic compounds. Chlorophyll contains magnesium whereas hemoglobin contails iron and hemocyanin copper. The color of these compounds is associated with the metal they contain; red for hemoglobin, green for chlorophyll and blue for hemocyanin. The function of chlorophyll is quite different from that of hemoglobin and hemacyanin. Chlorophyll is involved in the process of photosynthesis; hemaglobin and hemacyanin are carriers of oxygen.
Hemacyanin is the carrier of oxygen in haemalymph, the blood of arthropods. The arthropods phylum includes insects, arachnids (spiders) and crustaceans (lobsters, crabs, shrimp and other shell fish). Arthropods are in the Animal Kingdom, but, on the basis of their different chemistry from the other members of the Animal Kingdom whose chemistry is based upon Hemoglobin the arthopods could be considered a different life form; i.e., a separate kingdom. The physical structure of the of the arthropods is also quite different from that of other members of the Animal Kingdom; arthropods have an exoskeleton as oppoosed to the internal skeleton of vertebrates. A common theme of science-fiction is finding life forms on other planets whose chemistry is quite alien from ours. Well, such aliens are here and they are called arthropods.
The chemical formula for chlorophyll is relatively simple: C55H72O5N4Mg. In contrast the formula for hemoglobin is C2952H4664N812O832S8Fe4.
(To be continued.)
For other important metallo-organic molecules see Life Molecules II.
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