The purpose of starch biosynthesis in plants is to provide a store of
energy. Many plants have evolved to store large quantities of starch.
For example, near 90% of the dry weight consists of starch in rice grain
(Tian et al., 2009). The detail of starch biosynthesis is, however, more
complicated than this – involving a number of enzymes – but can be
summarized as follows. The process starts with combining of glucose-
1-phosphate with adenosine triphosphate (ATP) to form adenosine
diphosphate glucose (ADP-glucose), catalyzed by the enzyme AGPase.