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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.