B Amorphous regions A chains 6um B chains Crystalline regions Reducing end Hilum 6 D glucose units a1-→6 branch points Figure 3.2 Amylopectin and the starch granule.(A)The essential features of the cluster model first proposed by Robin in 1974.(B)The organisation of the amorphous and crystalline regions (or domains)of the structure generating the concentric layers that contribute to the 'growth rings'that are visible by light microscopy.(C)The orientation of the amylopectin molecules in a cross section of an idealised entire granule.(D)The likely double helix structure taken up by neighbouring chains and giving rise to the extensive degree of crystallinity in a granule