Polysaccharides: Difference between revisions

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Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

Karl Oberholser, Karsten Theis

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 === Unbranched, β(1→4) glycosidic bonds ===
-<scene name='Polysaccharides/Cellulose_1_chain/3'>Cellulose</scene><ref>[http://en.wikipedia.org/wiki/Cellulose Cellulose]</ref> is a polysaccharide with glucose units connected only by β(1→4) linkages, and therefore is unbranched. Notice that every other glucose residue is flipped 180° with respect to the preceding residue. This configuration can be best identified by observing on what side of the chain C-6 of glucose is located. Since the linkage is β, this configuration is necessary in order for the <scene name='Polysaccharides/Cellulose_1_chain2/5'>glycosidic oxygen</scene> to have its normal angular geometry. Observe that of the two residues highlighted the lower right one is flipped. Moving down the chain to the <scene name='Polysaccharides/Cellulose_1_chain3/1'>next linkage</scene> notice that the oxygen on C-1 having the β configuration projects down because the glucose residue has been flipped 180° and that the next residue in its normal orientation is properly positioned to bond with the oxygen forming the angular geometry for oxygen. <scene name='Polysaccharides/Cellulose_1_chain4/1'>Next residue</scene> is in the flipped position.
+[[Cellulose]] is a polysaccharide with glucose units connected only by β(1→4) linkages, and therefore is unbranched. A theoretical model of <scene name='Polysaccharides/Cellulose_1_chain/3'>cellulose</scene> illustrates the structural features. Notice that every other glucose residue is flipped 180° with respect to the preceding residue. This configuration can be best identified by observing on what side of the chain C-6 of glucose is located. Since the linkage is β, this configuration is necessary in order for the <scene name='Polysaccharides/Cellulose_1_chain2/5'>glycosidic oxygen</scene> to have its normal angular geometry. Observe that of the two residues highlighted the lower right one is flipped. Moving down the chain to the <scene name='Polysaccharides/Cellulose_1_chain3/1'>next linkage</scene> notice that the oxygen on C-1 having the β configuration projects down because the glucose residue has been flipped 180° and that the next residue in its normal orientation is properly positioned to bond with the oxygen forming the angular geometry for oxygen. <scene name='Polysaccharides/Cellulose_1_chain4/1'>Next residue</scene> is in the flipped position.
-Cellulose is present in a cell wall as a microfibril which is a paracrystalline structure containing 36 strands of cellulose. A brief description of the biosynthesis of this microfibril is at <ref>[http://en.wikipedia.org/wiki/Cellulose#Biosynthesis Cellulose biosynthesis]</ref><scene name='Polysaccharides/Cellulose_2_chains/1'>Show second chain</scene>
+Cellulose is present in a cell wall as a microfibril which is a paracrystalline structure containing 36 strands of cellulose. A brief description of the biosynthesis of this microfibril is available.<ref>[http://en.wikipedia.org/wiki/Cellulose#Biosynthesis Cellulose biosynthesis]</ref> During the synthesis of a single chain in order to achieve the configuration as described above,every other residue flipped 180°, the active site of the sythase has to accommodate two glucose molecules. One glucose molecule is flipped 180° with respect to the other one during bind to the active site, and the active site has the facility to catalyze the formation of two glycosidic bonds extending the chain by two glucose residues.<ref>complete</ref>
+<scene name='Polysaccharides/Cellulose_2_chains/1'>Show second chain</scene>