Estimations of the proportion of glucose residues present as end-groups in the amylopectin component of starch have shown that some 5 per cent of the glucose residues occur as terminal groups. Since amylopectin has a high molecular weight, of the order of 106, a branched-chain structure must be present in the molecule. The main features of the structure are indicated diagrammatically in Fig. 1 1, where (A), (B), (C), etc., are chains containing on