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. Rotate to view the glucopyranosyl units on edge to see that the bonds are α linkages. but its structure is more complex because it also contains α(1→ 6) glycosidic bonds. , branching point, colored yellow. The green ring is the reducing end of the molecule. The chain that proceeds from the branching point is colored blue. The yellow rings are the non-reducing ends of the two branches. They just happen to be close to each other in this model. The structure is more open (helix is not wound as tight) than the amylose because more space is needed for the chain that is formed at the branching point. 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.