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    Hi guys, so the wording of this doesn't make sense: "The monomers of N-acetylglucosamine join by 1-4 glycosidic bonds to form the chitin molecule."
    Shouldn't it be the monomers of chitin which are N-acetylglucosamine molecules join by 1-4 glycosidic bonds to form the chitin molecule - because the monomers of N-acetylglucosamine are what makes up the N-acetylglucosamine molecule not the chitin molecule.
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    Hi I think with the deterioration of the teaching of English in recent years, the examiner themselves are stating this Q in a confusing way - when they say the "monomers of N-acetylglucosamine.............." , what they are trying to say is "the monomers, namely N-acetylglucosamine...........".

    Yes, I don't blame you at all for being struck by this error in grammar on the part of the examiner:-

    If you look at the structure of N-acetylglucosamine (which is given), it is basically a glucose molecule with an acetyl group............:

    O
    ||
    C-CH3
    |
    N

    ...............in which one oxygen atom has been replaced by a nitrogen atom hence N-acetyl

    So, when several of these N-acetylglucosamine molecules join up by 1-4 glycosidic bonds (the -OH groups at the 1 and 4 positions unite dropping off H2O (= condensation reaction) forming -O- (the same bond that makes straight chain polysachharides from glucose monomers - [branching occurs by the formation of 1-6 bonds as in glycogen])), you get chitin, analogous to the formation of the polysaccharide amylose from glucose monomers (the main difference being the lack of N-acetyl groups in the latter, effectively the absence of nitrogen)

    I think I can safely say that your English is better than the examiner's - just try to take current exam Qs with a pinch of salt!

    M (specialist biology tutor)

    BTW - chitin is also the main constituent of the cell wall of fungal cells.
 
 
 
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