Chitin

From Palaeos

A polymer of repeating sugar molecules (a slightly modified glucose, poly-N-acetyl-D-glucosamine). See image. Chitin is the material which makes up the exoskeletons of insects and other arthropods. In arthropods, chitin occurs in a crosslinked form, α-chitin, and is strengthened with the additions of structural proteins and calcium carbonate salts. Significantly, it is also found in the radular "teeth" and operculums of molluscs, the setae (bristles) and jaws of annelid worms, and the cell walls of Fungi. So, this is exceedingly ancient stuff, predating the split between animals, fungi and protists and possibly even predating the split between bacteria and metazoans. [What may be of sociological interest is that the 1,5 aldose linkage was missing from the middle glucose in this diagram and no one spotted it for over a year ....]

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ATW?