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  • Created on: 18-03-13 21:14
Preview of CELLULOSE (snab)

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A polysaccharide made up of BETA GLUCOSE MOLECULES.
A CONDENSATION REACTION between the ­OH group on the first carbon of one glucose and the ­OH on the fourth carbon of an adjacent glucose
molecule links the 2 molecules. A 1, 4 glycosidic bond forms.
There are none of the 1, 6 bonds that occur in Starch which are made up of alpha glucose molecule. Therefore, cellulose is a long, unbranched molecule.
Unlike an amylase molecule which winds into a spiral, the cellulose molecules remain as straight chains.
Hydrogen bonds form between the ­OH groups in neighbouring cellulose chains, forming bundles called MICROFIBRILS.
Individually, the hydrogen bonds are weak compared with glycosidic bonds however the large amount of hydrogen bonds together produce a strong
The arrangement of cellulose microfibrils in plant cell walls
The microfibrils are wound in a helical arrangement around the cell and stuck together with polysaccharide glue (hemicelluloses and pectins) Pectins act
as cement and hold the cells together.
The arrangement of the cellulose microfibrils within a matrix of hemicelluloses and pectins makes the wall very strong.
The microfibrils are laid down at different angles (forming a net-like structure), which make the wall strong and flexible.
The SECONDARY THICKENING of cell walls also makes them strong.
When some structural plant cells have finished growing, they produce a secondary cell wall between the normal cell wall and the cell membrane. This new
wall is usually thicker and contains more lignin.


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