Polysaccharides

Unbranched chain, α(1→4) glycosidic bonds

Amylose is an example of a polysccharide which contains thousands of glucoses connected by α(1→4) glycosidic bonds. The initial view () shows an eleven unit segment of amylose with yellow halos marking some of the oxygens which form the 1→4 glycosidic bonds. Rotate to view the glucopyranosyl units on edge to see that the bonds are α linkages. (Remember: With the glucose providing C-1 on the left, the glucose providing C-4 on the right and C-6 of the glucoses projecting to the back of the screen both bonds of the oxygen of the α linkage project down.) From this perspective you are looking down the axis of a helix that is formed as a result of the angle that is form between the glucopyranosyl residues when they are connected by the α(1→4) bonds. This characteristic of the α(1→4) bond was seen when studying maltose. ends of the polymer yellow and green. with 20 glucose units;

Branched chain, α(1→4) glycosidic bonds

is also a large glucose polymer that has α(1→4) glycosidic bonds connecting the glucose units, but it also contains α(1→ 6) glycosidic bonds. In this scene the main branch is colored yellow, the side branch is green and the oxygen atoms of the α(1→4) bonds are red. Rotate to view the glucopyranosyl units on edge and verify that the bonds are α linkages. , branching point, colored yellow with the oxygen atom connecting C-6 of unit four to the C-1 of the side chain colored green. The is colored CPK, C-1 of this unit is able to open to the aldehyde and function as a reducing agent, but all the other termini of an amylopectin molecule are non-reducing because the C-1 of these terminal units are involved in glycosidic bond and can not form the aldehyde. In this scene the non-reducing termini are colore green. The native amylopectin having many more branching points would be more open than this structure, in fact it would have very little curvature. Rotating & zooming amylopectin gives a focused view of the α(1→ 6) bond.