Starch
Amylose |
Amylopectin |
Amylose is a polysaccharide made up of Alpha glucose molecules.
Each of the molecules is linked by 1,4 Glycosidic bonds. This results in a long chain of glucose molecules. Because there is a slight 'bend' in the glycosidic bond the molecule coils into a helix shape (as shown). This is useful because it results in a very compact molecule that is ideal for storage. However, when the molecule needs to be broken down to release it's energy this shape become a hindrance. Amylase (the enzyme that breaks it down) only works on the ends. So energy is released slowly. |
Amylopectin is also a polysaccharide made up entirely of alpha glucose molecules. In this instance though, both 1,4 Glycosidic bonds and 1,6 Glycosidic bonds occur.
The 1,6 Glycosidic bonds result in new 'branches'. These occur on around every 20 molecules of glucose. This branching makes the molecule much less compact than amylose so less energy can be stored in a certain amount of space. The advantage is that amylase can now work on multiple 'ends' all at once. Therefore amylopectin can release its energy much more quickly. |
Typically starch will be made up of around 20% Amylose and 80% Amylopectin, but, this varies from one plant/food source to another.