This structure is distinguishable from the correct structure by a more haphazard appearance, without a clear distinction between A and B chains, with variable chain lengths and with more than or less than two branch points per B-chain. In addition, of course, the glycogenin molecule at the core is omitted, as this was not suspected in 1940. What the textbooks say All of the textbooks examined either give the incorrect structure or show the structure so vaguely that it is difficult to guess whether it is based on the correct one or not. If they mention glycogenin at all they do so in a different context from the one in which the structure is given. If the average chain length were much greater or much shorter, glycogen would not be as efficient a vehicle for energy storage and release on demand.
Experimental results support the conclusions reached from the mathematical modeling.
The synthase-glycogenin interaction limits the size of glycogen granules. We see here a simple and elegant molecular device for setting the size of a biological structure. It is not explained how a small 38 kDa protein buried deep inside a 1000 kDa polymer can remain in contact with an enzyme working on the surface. As this book was not among those I had easy access to when making the original survey it is not at present included in these pages. However, I shall try to include it when I have more information about the other questions considered.