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    https://b26cc0cff3cb5180558ef6ab4ced...%20Biology.pdf

    In 2b ii) of this question, the carbohydrate present in the exoskeleton would be chitin right? Although in the question its just carbohydrate but in 2bii) where it asks about how the molecules give strength to the exoskeleton. I thought chitin forms a heteropolysaccharide which makes the exoskeleton waterproof and tough.

    However the answer in the mark scheme seems to be describing cellulose....

    Here is the answer:
    Any two fromAlternating molecules rotated through 180º form straightchains;{Cross links/hydrogen bonds/ H bonds} form between chains;forming microfibrils;
    I thought only bonds in cellulose rotate, not chitin... Also, why can't starch form microfibrils?
    Thank you.
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    (Original post by coconut64)
    https://b26cc0cff3cb5180558ef6ab4ced...%20Biology.pdf

    In 2b ii) of this question, the carbohydrate present in the exoskeleton would be chitin right? Although in the question its just carbohydrate but in 2bii) where it asks about how the molecules give strength to the exoskeleton. I thought chitin forms a heteropolysaccharide which makes the exoskeleton waterproof and tough.

    However the answer in the mark scheme seems to be describing cellulose....

    Here is the answer:
    Any two fromAlternating molecules rotated through 180º form straightchains;{Cross links/hydrogen bonds/ H bonds} form between chains;forming microfibrils;
    I thought only bonds in cellulose rotate, not chitin... Also, why can't starch form microfibrils?
    Thank you.
    Chitin is not a heteropolysaccharide, it's only made from one type of monomer. Bonds in cellulose rotate but so does chitin (its a case of using the information you're given to be able to answer the question).
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    (Original post by RMNDK)
    Chitin is not a heteropolysaccharide, it's only made from one type of monomer. Bonds in cellulose rotate but so does chitin (its a case of using the information you're given to be able to answer the question).
    Hi, so only beta glucose molecules can rotate? And yes I realise that chitin is a polysaccharide now thanks. But in my textbook it says something about a group being replaced to form a heteropolysaccharde. What does that mean?? Also, when you say using the information given to answer the question, how could you possibly do that? I don't really know what you mean as there is very little hint given. Thanks
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    (Original post by coconut64)
    Hi, so only beta glucose molecules can rotate? And yes I realise that chitin is a polysaccharide now thanks. But in my textbook it says something about a group being replaced to form a heteropolysaccharde. What does that mean?? Also, when you say using the information given to answer the question, how could you possibly do that? I don't really know what you mean as there is very little hint given. Thanks
    Yes I think so, only beta glucose rotates.

    Well if you look on the diagram, the polysaccharide unit isn't purely like the units you've seen. There's some groups been substituted like NHCOCH3 which is why chitin is said to be a derivative of glucose. I still don't understand why your book says its a heteropolysaccharide because to be a heteropolysaccharide you have to be made from two or more different monosaccharides.


    Well, you can look at the diagram and see that one of the monomer units has rotated. You gotta make that link with cellulose. If you didn't know about chitin, but you knew about cellulose, then you knew that cellulose was strong due to the cross links formed between polysaccharide chains of beta glucose that are side to side, as well as the staggered ends between adjacent chains.
    Similarly, you can apply the same reasoning to this polysaccharide; one has rotated, ah perhaps it's like cellulose.
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    (Original post by RMNDK)
    Yes I think so, only beta glucose rotates.

    Well if you look on the diagram, the polysaccharide unit isn't purely like the units you've seen. There's some groups been substituted like NHCOCH3 which is why chitin is said to be a derivative of glucose. I still don't understand why your book says its a heteropolysaccharide because to be a heteropolysaccharide you have to be made from two or more different monosaccharides.


    Well, you can look at the diagram and see that one of the monomer units has rotated. You gotta make that link with cellulose. If you didn't know about chitin, but you knew about cellulose, then you knew that cellulose was strong due to the cross links formed between polysaccharide chains of beta glucose that are side to side, as well as the staggered ends between adjacent chains.
    Similarly, you can apply the same reasoning to this polysaccharide; one has rotated, ah perhaps it's like cellulose.
    Name:  1456671725503-574574579.jpg
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Size:  319.1 KB this is what it says in my textbook and thanks! I get what you mean now.
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    (Original post by coconut64)
    Name:  1456671725503-574574579.jpg
Views: 55
Size:  319.1 KB this is what it says in my textbook and thanks! I get what you mean now.
    No problem.

    And honestly I think your textbook is wrong. You can find online loads of websites and sources that say it's a homopolysaccharide.
    It's only got that one repeating unit: the carbon ring with that acetylamine group

    Perhaps your spec says otherwise or your teacher says otherwise as well.
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    (Original post by RMNDK)
    No problem.

    And honestly I think your textbook is wrong. You can find online loads of websites and sources that say it's a homopolysaccharide.
    It's only got that one repeating unit: the carbon ring with that acetylamine group

    Perhaps your spec says otherwise or your teacher says otherwise as well.
    Oh really? I have no idea then, just gonna to follow what it says. Could you possibly help me out in the other thread as well? The one about transpiration. Thanks!
 
 
 
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