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    Hi, I am a bit confused about the answer for this question:

    Explain how the structures of starch and cellulose are related to their functions asstorage and structural molecules respectively.

    My answer is:
    -starch has two polymers which are amylose and amylopectin. Amylopectin molecules are compact and can coil into alpha helices in a small space. Hence starch is an energy storage in plants.

    - long parallel chains are crossed linked by hydrogen bonds in cellulose forming microfibrils. Hence, cellulose is present in plant cell wall as cellulose gives rigidity and structural stability to cell wall. Hence the cell wall can resist turgor.

    This is the mark scheme:
    Starch: any 2correct reference to amylose and/or amylopectin;glycosidic bonds (α 1-4);molecules coil/branch (in amylopectin);NOT compact
    NOT: amylopectin – coiled or amylase branched easy to add/remove {glucose / maltose} units;

    2Cellulose: any 2alternate units rotate / head up, head down / 180q rotation;straight chain only / no branches; NOT parallel hydrogen bonds between / reference to cross linking;gives strength or stability / forming microfibrils;

    The parts in bold are clearly contradicting my answer, but in my text book it mentions that cellulose has long parallel chains though... Also do i say starch can coil, rather than amylopectin molecule can coil? Thanks!
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    I have made a few corrections:

    - Amylose forms a chain which can coil into an alpha helix. Hence, amylose is a compact molecules and therefore a great energy storage
    - amylopectin has branches which are linked by 1,6-glycosidic bonds. Hence, alpha glucose molecules can be hydrolysed rapidly, so the rapid release of glucose for respiration makes starch a good energy storage.

    Is this right?
 
 
 
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