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The Cellulose Cell WallLearning objectives:
1. To be able to describe the structure of cellulose.2. To be able to compare the structure of cellulose and
starch.
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Starter activity- Starch
Write down all the key points youremember about the structure of starch.
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The chemistry of celluloseellulose is an unbranched chain of glucose units.!ade of a different form of glucose than that of
starch" it comprises of beta glucose units #starch ismade of alpha glucose units$.
What do you notice about the glucose units%
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The chemistry of cellulose
The glucose units in cellulose join by losing a watermolecule in a condensation reaction& and comprise of1&' glycosidic bonds between beta(glucose molecules.
This is only possible if every other molecule is rotated
1)* degrees.This allows it to be a straight unbranched chain.
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Cellulose Vs Starch
+raw a table& showing the differencesbetween the structure of cellulose and
starch.
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MicrofibrilsLong straight chains
then naturally packtogether in bundlesand held together by
hydrogen bonds.These are microfibrils.
The hydrogen bonds
form between the ,-groups inneighbouring cellulosechains.
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Microfibrils
The layers of microfibrils then layer over eachother at angles to one another& forming a
complete structure.
The substance that holds these microfibrilstogether is a short& branched polysaccharide
called hemicelluloses and pectins.
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Pectins
sing pages 1/'(1/0 in orange books&write down some uses for pectins in plantsand in the industry.
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Plasmodesmata
arrow fluid(filled channels crossing thecells walls.These allow substances to move freely
between cells and make cell walls fullypermeable.
Where are
plasmodesmatalocated%
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Pits
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Check your learning
Learning objectives:
1. To be able to describe the structure ofcellulose.
2. To be able to compare the structure of
cellulose and starch.